Light steering device with an array of oscillating reflective slats

ABSTRACT

A light detection and ranging (LIDAR) device scans through a scanning zone while emitting light pulses and receives reflected signals corresponding to the light pulses. The LIDAR device scans the emitted light pulses through the scanning zone by reflecting the light pulses from an array of oscillating mirrors. The mirrors are operated by a set of electromagnets arranged to apply torque on the mirrors, and an orientation feedback system senses the orientations of the mirrors. Driving parameters for each mirror are determined based on information from the orientation feedback system. The driving parameters can be used to drive the mirrors in phase at an operating frequency despite variations in moments of inertia and resonant frequencies among the mirrors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/813,320, filed Jul. 30, 2015, which is a continuation of U.S. patentapplication Ser. No. 14/090,485, filed Nov. 26, 2013, which claimspriority to U.S. Provisional Patent Application No. 61/773,573, filedMar. 6, 2013. These applications are incorporated herein by reference intheir entirety and for all purposes.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Vehicles can be configured to operate in an autonomous mode in which thevehicle navigates through an environment with little or no input from adriver. Such autonomous vehicles can include one or more sensors thatare configured to detect information about the environment in which thevehicle operates. The vehicle and its associated computer-implementedcontroller use the detected information to navigate through theenvironment. For example, if the sensor(s) detect that the vehicle isapproaching an obstacle, as determined by the computer-implementedcontroller, the controller adjusts the vehicle's directional controls tocause the vehicle to navigate around the obstacle.

One such sensor is a light detection and ranging (LIDAR) device. A LIDARactively estimates distances to environmental features while scanningthrough a scene to assemble a cloud of point positions indicative of thethree-dimensional shape of the environmental scene. Individual pointsare measured by generating a laser pulse and detecting a returningpulse, if any, reflected from an environmental object, and determiningthe distance to the reflective object according to the time delaybetween the emitted pulse and the reception of the reflected pulse. Thelaser, or set of lasers, can be rapidly and repeatedly scanned across ascene to provide continuous real-time information on distances toreflective objects in the scene. Combining the measured distances andthe orientation of the laser(s) while measuring each distance allows forassociating a three-dimensional position with each returning pulse. Athree-dimensional map of points of reflective features is generatedbased on the returning pulses for the entire scanning zone. Thethree-dimensional point map thereby indicates positions of reflectiveobjects in the scanned scene.

SUMMARY

A beam-steering device for a light detection and ranging (LIDAR) deviceis disclosed. The LIDAR device scans through a scanning zone whileemitting light pulses and receives reflected signals corresponding tothe light pulses. The emitted light pulses are scanned through thescanning zone by reflecting the light from an array of oscillatingmirrors. The mirrors are driven by a set of electromagnets arranged toapply torque on the mirrors, and an orientation feedback system sensesthe orientations of the mirrors. Driving parameters for each mirror aredetermined based on information from the orientation feedback system.The drying parameters can be used to drive the mirrors in phase at anoperating frequency despite variations in moments of inertia andresonant frequencies among the mirrors.

Some embodiments of the present disclosure provide a light detection andranging (LIDAR) device. The LIDAR device can include a plurality ofmirrors arranged to rotate about respective axes of rotation parallel toa reflective surface of the respective mirrors. The axes of rotation ofthe plurality of mirrors can be arranged to be aligned in parallel andin a common plane. The LIDAR device can include a plurality ofelectromagnets arranged to attract the plurality of mirrors via inducedmagnetic fields generated in the mirrors so as to apply torque on therespective mirrors about their respective axes of rotation. Each of theplurality of electromagnets can be arranged to apply torque to only oneof the plurality of mirrors such that each of the plurality of mirrorsis associated with a mirror-associated set of electromagnets in theplurality of electromagnets. The LIDAR device can include a plurality ofdriving circuits for operating the plurality of electromagnets using aplurality of driving signals. Each driving circuit can be configured toreceive a respective input and generate, based on the respective input,a respective driving signal for operating a respective mirror-associatedset of electromagnets. The LIDAR device can include a plurality ofdetectors configured to detect orientations of the plurality of mirrors.The LIDAR device can include a controller configured to: (i) receivedata from the plurality of detectors indicative of detected orientationsof the plurality of mirrors, (ii) determine, based on the detectedorientations, driving parameters sufficient to cause the plurality ofdriving circuits to operate the plurality of electromagnets such thatthe plurality of mirrors oscillate in phase at an operating frequency,and (iii) provide the determined driving parameters as input to theplurality of driving circuits. The LIDAR device can include a lightsource configured to emit light pulses directed toward the plurality ofmirrors such that the light pulses are reflected by the plurality ofmirrors.

Some embodiments of the present disclosure provide a method. The methodcan include operating a plurality of sets of mirror-associatedelectromagnets such that each set of mirror-associated electromagnets isoperated by a respective driving circuit in a plurality of drivingcircuits based on respective input. Each set of mirror-associatedelectromagnets can be configured to apply torque to a respective mirrorin a plurality of mirrors so as to cause the respective mirror to rotateabout a respective axis of rotation parallel to a reflective surface ofthe respective mirror. The plurality of mirrors can have axes ofrotation aligned in parallel and in a common plane. The method caninclude receiving, from a plurality of detectors configured to detectorientations of the plurality of mirrors, data indicative of detectedorientations of the plurality of mirrors. The method can includedetermining, based on the detected orientations, driving parameterssufficient to cause the plurality of driving circuits to operate theplurality of electromagnets such that the plurality of mirrors oscillatein phase at an operating frequency. The method can include providing thedetermined driving parameters as input to the plurality of drivingcircuits.

Some embodiments of the present disclosure provide a non-transitorycomputer readable medium storing instructions that, when executed by oneor more processors in a computing device, cause the computing device toperform operations. The operations can include operating a plurality ofsets of mirror-associated electromagnets such that each set ofmirror-associated electromagnets is operated by a respective drivingcircuit in a plurality of driving circuits based on respective input.Each set of mirror-associated electromagnets can be configured to applytorque to a respective mirror in a plurality of mirrors so as to causethe respective mirror to rotate about a respective axis of rotationparallel to a reflective surface of the respective mirror. The pluralityof mirrors can have axes of rotation aligned in parallel and in a commonplane. The operations can include receiving, from a plurality ofdetectors configured to detect orientations of the plurality of mirrors,data indicative of detected orientations of the plurality of mirrors.The operations can include determining, based on the detectedorientations, driving parameters sufficient to cause the plurality ofdriving circuits to operate the plurality of electromagnets such thatthe plurality of mirrors oscillate in phase at an operating frequency.The operations can include providing the determined driving parametersas input to the plurality of driving circuits.

Some embodiments of the present disclosure provide a means foroscillating a plurality of mirrors such that the plurality of mirrorsoscillate in phase at an operating frequency.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a functional block diagram depicting aspects of an exampleautonomous vehicle.

FIG. 2 depicts exterior views of an example autonomous vehicle.

FIG. 3 is a block diagram of an example light detection and ranging(LIDAR) system.

FIG. 4A is a diagram of an example LIDAR system that scans a scanningzone via an oscillating mirror.

FIG. 4B is a diagram of an example LIDAR system that employs multiplelight sources reflected from an oscillating mirror to scan a scanningzone.

FIG. 5A is an aspect view of an example beam-steering device havingmultiple oscillating reflective slats.

FIG. 5B is a top view of the example beam-steering device shown in FIG.5A.

FIG. 5C is an end view of the example beam-steering device shown in FIG.5A.

FIG. 5D is a cross-sectional side view of one of the reflective slatsthat shows example electromagnets associated with the reflective slat.

FIG. 6A is an end view of a reflective slat oriented in a nominalposition, according to an example embodiment.

FIG. 6B is an end view of a reflective slat oriented in a rotatedposition due to attraction between the slat and an electromagnet,according to an example embodiment.

FIG. 6C is an end view of the reflective slat oriented in a secondrotated position due to the reflexive torque applied by the connectingarm, according to an example embodiment.

FIG. 7 is a view of a beam-steering device with multiple oscillatingreflective slats, according to an example embodiment.

FIG. 8A is a block diagram of an electromagnetic driving system for abeam-steering device with multiple oscillating mirrors, according to anexample embodiment.

FIG. 8B is a block diagram of an electromagnetic driving system thatincludes inductance sensors to detect the orientations of multipleoscillating mirrors, according to an example embodiment.

FIG. 9A is a flowchart of a process for operating a beam-steering devicewith multiple oscillating mirrors according to an example embodiment.

FIG. 9B is a flowchart of a process for operating a LIDAR deviceaccording to an example embodiment.

FIG. 10 depicts a non-transitory computer-readable medium configuredaccording to an example embodiment.

DETAILED DESCRIPTION

Example embodiments relate to an autonomous vehicle, such as adriverless automobile, that includes a light detection and ranging(LIDAR) sensor for actively detecting reflective features in theenvironment surrounding the vehicle. A controller analyzes informationfrom the LIDAR sensor to identify the surroundings of the vehicle. Eachdistance measurement of a scanning LIDAR is associated with a point or“spot” on a reflective feature. Scanning the LIDAR through a range oforientations provides a three-dimensional distribution of reflectivepoints, which is referred to herein as a 3-D point map or 3-D pointcloud.

According to some embodiments, a LIDAR device includes one or morepulsing lasers directed toward an array of oscillating mirrors. Theindividual mirrors are each smaller than the cross-section of a singleincident laser beam, but are spaced closely such that incident laserbeams are jointly reflected by a plurality of the mirrors. The mirrorsare driven to oscillate in phase such that a laser beam pulse reflectedby the array of mirrors is substantially reflected all in the samedirection. Oscillating the array of mirrors directs the pulses of laserlight to scan across a scanning zone surrounding the LIDAR device. Theemitted pulses of laser light are then reflected by the environmentalsurroundings and the reflected light is detected by a light sensorassociated with the LIDAR. The time delay between emitting the pulse oflaser light and receiving the returning reflected signal provides anindication of the distance to a reflective feature, while theorientation of the mirrors in the array of mirrors indicates thedirection to the reflective feature.

In contrast to a single solid mirror, an array of mirrors can beoscillated at a much higher frequency than a single large mirror ofcomparable dimension. In particular, the individual small mirrors in thearray have correspondingly small moments of inertia. Thus, the array ofmirrors can span a region of about 3 centimeters by 5 centimeters andmay be driven at a frequency of 5 kilohertz, for example, withoutsignificant mechanical deformation to the reflective surfaces. Theindividual mirrors can be driven to oscillate so as to scan reflectedlight through an approximately 2 degree range of orientations (e.g., byoscillating plus or minus 1 degree).

The individual mirrors in the array can be driven by oscillatingelectromagnetic forces. For example, each mirror can be formed of aferromagnetic material, such as steel or another suitable metal, andelectromagnets can be situated near the back, opposite the reflectivesurface of the mirror, and close to a side edge distant from the axis ofrotation of the mirror. Energizing the electromagnets induces a magneticresponse in the ferromagnetic material of the mirror to urge the sideedge of the mirror toward the electromagnets, thereby rotating themirror about its axis of rotation and adjusting the orientation of themirror. Turning off the electromagnets relieves the torque on themirror. In some instances, one or more matching electromagnets can besituated near the opposing side edge of the mirror to attract the mirrorto rotate in the opposite direction following the initial rotation. Insome instances, the mirror can be biased in a non-rotated position(e.g., by a damping force such as a rigid axis of rotation, springs,etc.) such that turning off the electromagnets causes the mirror torotate back toward its non-rotated position. Such a restorative bias mayalso cause the mirror to over-rotate past its non-rotated position so asto oscillate the mirror in the opposite direction before rotating backtoward the electromagnets. Upon the side edge closest to theelectromagnets approaching the electromagnets, the electromagnets can beturned on again to attract the mirror in that direction. Repeating theprocess above can allow the mirror to oscillate.

In one configuration, a plurality of roughly rectangular steel mirrorsis suspended over a printed circuit board with their respectivereflective surfaces facing away from the printed circuit board. Eachmirror can have a rectangular shape with a pair of opposing short sidesand a pair of opposing long sides. Each mirror can be suspended over theprinted circuit board by narrow strips of metal connected to themidpoints of the short sides. The narrow strips (or connecting arms)connected to a mirror can be integrally formed with that mirror. Theconnecting arms flex, in a torsional direction, (i.e., twist) to allowthe mirrors to rotate about an axis of rotation defined by theconnecting arms. Tension in the connecting arms provides a restorativeforce biasing the mirrors in a flat, non-rotated position where theconnecting arms are in an untwisted, relaxed state.

The rectangular mirrors can be arranged with their respective axes ofrotation aligned in parallel and oriented in a common plane. Thus, eachrectangular mirror can have at least one long side adjacent the longside of a neighboring mirror, with a sufficient separation betweenneighboring mirrors to avoid interference during oscillation. Whiledriven, the array of mirrors can oscillate with the respective longsides of the respective rectangular mirrors moving up and down withrespect to the common plane defined by the axes of rotation.

The mirrors can be oscillated via electromagnets in the printed circuitboard located under the array of mirrors. In some examples, pairs ofsteel pegs extend from the printed circuit board substantiallyperpendicular to the back surfaces of the mirrors. Each pair of steelpegs terminates proximate the back surface of one of the mirrors near along side of the mirror and offset from the mirror's axis of rotation.Each peg is surrounded by a conductive coil created by traces in theprinted circuit board. Driving current through the traces turns on theelectromagnets and the respective pegs are the ferromagnetic cores ofthe electromagnets. Driving the electromagnets with a periodic currentprovides a corresponding periodic attractive force between the edges ofthe mirrors and the pegs to cause the mirrors to oscillate.

In an example, the individual mirrors and connecting arms are cut from asingle plate of silicon steel such that the connecting arms connect themirrors to an outer frame.

Feedback sensors are included to monitor the positions of the individualmirrors and adjust the amplitude and/or phase of the driving signalssuch that the entire array of mirrors oscillates in phase. Inparticular, deviations in the amplitude and/or phase of oscillations inindividual mirrors may occur due to variations in resonant frequenciesand/or moments of inertia among the individual mirrors. The amplitudeand phase of the oscillations of the mirrors are each dependent on theinherent resonant frequency and/or moment of inertia of the individualmirrors, which is a function of the precise device parameters (materialproperties, mass distribution, dimensions, etc.), which may varysomewhat among the mirrors due to manufacturing variations, etc. Whilethe input driving frequency may be fixed across the array, the relativephase and/or amplitude of the electromagnet driving signals for eachmirror can be tuned for the electromagnets associated with each mirrorto account for variations in resonant frequencies. For example, amicrocontroller can evaluate information from the feedback sensors andadjust the phase and/or amplitude of the electromagnet driver signalsapplied to electromagnets associated with each mirror to compensate fordetected phase offsets between mirrors.

The feedback information may be provided by monitoring the impedancebetween matching pairs of pegs in the electromagnets. The impedance insuch a “magnetic circuit” is related to the gap distance between theends of the pegs and the respective back sides of the mirrors. Thus,monitoring the impedance value provides an indication of the orientationof the mirrors. The feedback information may additionally oralternatively be provided by an optical sensing system that illuminatesthe mirrors with a light source and detects the light with aphoto-sensitive detector in a fixed position to determine theorientation of the mirror.

In example embodiments, the example system may include one or moreprocessors, one or more forms of memory, one or more inputdevices/interfaces, one or more output devices/interfaces, andmachine-readable instructions that when executed by the one or moreprocessors cause the system to carry out the various functions, tasks,capabilities, etc., described above.

Some aspects of the example methods described herein may be carried outin whole or in part by an autonomous vehicle or components thereof.However, some example methods may also be carried out in whole or inpart by a system or systems that are remote from an autonomous vehicle.For instance, an example method could be carried out in part or in fullby a server system, which receives information from sensors (e.g., rawsensor data and/or information derived therefrom) of an autonomousvehicle. Other examples are also possible.

Example systems within the scope of the present disclosure will now bedescribed in greater detail. An example system may be implemented in, ormay take the form of, an automobile. However, an example system may alsobe implemented in or take the form of other vehicles, such as cars,trucks, motorcycles, buses, boats, airplanes, helicopters, lawn mowers,earth movers, boats, snowmobiles, aircraft, recreational vehicles,amusement park vehicles, farm equipment, construction equipment, trams,golf carts, trains, and trolleys. Other vehicles are possible as well.

FIG. 1 is a functional block diagram illustrating a vehicle 100according to an example embodiment. The vehicle 100 is configured tooperate fully or partially in an autonomous mode, and thus may bereferred to as an “autonomous vehicle.” For example, a computer system112 can control the vehicle 100 while in an autonomous mode via controlinstructions to a control system 106 for the vehicle 100. The computersystem 112 can receive information from one or more sensor systems 104,and base one or more control processes (such as setting a heading so asto avoid a detected obstacle) upon the received information in anautomated fashion.

The autonomous vehicle 100 can be fully autonomous or partiallyautonomous. In a partially autonomous vehicle some functions canoptionally be manually controlled (e.g., by a driver) some or all of thetime. Further, a partially autonomous vehicle can be configured toswitch between a fully-manual operation mode and a partially-autonomousand/or a fully-autonomous operation mode.

The vehicle 100 includes a propulsion system 102, a sensor system 104, acontrol system 106, one or more peripherals 108, a power supply 110, acomputer system 112, and a user interface 116. The vehicle 100 mayinclude more or fewer subsystems and each subsystem can optionallyinclude multiple components. Further, each of the subsystems andcomponents of vehicle 100 can be interconnected and/or in communication.Thus, one or more of the functions of the vehicle 100 described hereincan optionally be divided between additional functional or physicalcomponents, or combined into fewer functional or physical components. Insome further examples, additional functional and/or physical componentsmay be added to the examples illustrated by FIG. 1.

The propulsion system 102 can include components operable to providepowered motion to the vehicle 100. In some embodiments the propulsionsystem 102 includes an engine/motor 118, an energy source 119, atransmission 120, and wheels/tires 121. The engine/motor 118 convertsenergy source 119 to mechanical energy. In some embodiments, thepropulsion system 102 can optionally include one or both of enginesand/or motors. For example, a gas-electric hybrid vehicle can includeboth a gasoline/diesel engine and an electric motor.

The energy source 119 represents a source of energy, such as electricaland/or chemical energy, that may, in full or in part, power theengine/motor 118. That is, the engine/motor 118 can be configured toconvert the energy source 119 to mechanical energy to operate thetransmission. In some embodiments, the energy source 119 can includegasoline, diesel, other petroleum-based fuels, propane, other compressedgas-based fuels, ethanol, solar panels, batteries, capacitors,flywheels, regenerative braking systems, and/or other sources ofelectrical power, etc. The energy source 119 can also provide energy forother systems of the vehicle 100.

The transmission 120 includes appropriate gears and/or mechanicalelements suitable to convey the mechanical power from the engine/motor118 to the wheels/tires 121. In some embodiments, the transmission 120includes a gearbox, a clutch, a differential, a drive shaft, and/oraxle(s), etc.

The wheels/tires 121 are arranged to stably support the vehicle 100while providing frictional traction with a surface, such as a road, uponwhich the vehicle 100 moves. Accordingly, the wheels/tires 121 areconfigured and arranged according to the nature of the vehicle 100. Forexample, the wheels/tires can be arranged as a unicycle, bicycle,motorcycle, tricycle, or car/truck four-wheel format. Other wheel/tiregeometries are possible, such as those including six or more wheels. Anycombination of the wheels/tires 121 of vehicle 100 may be operable torotate differentially with respect to other wheels/tires 121. Thewheels/tires 121 can optionally include at least one wheel that isrigidly attached to the transmission 120 and at least one tire coupledto a rim of a corresponding wheel that makes contact with a drivingsurface. The wheels/tires 121 may include any combination of metal andrubber, and/or other materials or combination of materials.

The sensor system 104 generally includes one or more sensors configuredto detect information about the environment surrounding the vehicle 100.For example, the sensor system 104 can include a Global PositioningSystem (GPS) 122, an inertial measurement unit (IMU) 124, a RADAR unit126, a laser rangefinder/LIDAR unit 128, a camera 130, and/or amicrophone 131. The sensor system 104 could also include sensorsconfigured to monitor internal systems of the vehicle 100 (e.g., O₂monitor, fuel gauge, engine oil temperature, wheel speed sensors, etc.).One or more of the sensors included in sensor system 104 could beconfigured to be actuated separately and/or collectively in order tomodify a position and/or an orientation of the one or more sensors.

The GPS 122 is a sensor configured to estimate a geographic location ofthe vehicle 100. To this end, GPS 122 can include a transceiver operableto provide information regarding the position of the vehicle 100 withrespect to the Earth.

The IMU 124 can include any combination of sensors (e.g., accelerometersand gyroscopes) configured to sense position and orientation changes ofthe vehicle 100 based on inertial acceleration.

The RADAR unit 126 can represent a system that utilizes radio signals tosense objects within the local environment of the vehicle 100. In someembodiments, in addition to sensing the objects, the RADAR unit 126and/or the computer system 112 can additionally be configured to sensethe speed and/or heading of the objects.

Similarly, the laser rangefinder or LIDAR unit 128 can be any sensorconfigured to sense objects in the environment in which the vehicle 100is located using lasers. The laser rangefinder/LIDAR unit 128 caninclude one or more laser sources, a laser scanner, and one or moredetectors, among other system components. The laser rangefinder/LIDARunit 128 can be configured to operate in a coherent (e.g., usingheterodyne detection) or an incoherent detection mode.

The camera 130 can include one or more devices configured to capture aplurality of images of the environment surrounding the vehicle 100. Thecamera 130 can be a still camera or a video camera. In some embodiments,the camera 130 can be mechanically movable such as by rotating and/ortilting a platform to which the camera is mounted. As such, a controlprocess of vehicle 100 may be implemented to control the movement ofcamera 130.

The sensor system 104 can also include a microphone 131. The microphone131 can be configured to capture sound from the environment surroundingvehicle 100. In some cases, multiple microphones can be arranged as amicrophone array, or possibly as multiple microphone arrays.

The control system 106 is configured to control operation(s) regulatingacceleration of the vehicle 100 and its components. To effectacceleration, the control system 106 includes a steering unit 132,throttle 134, brake unit 136, a sensor fusion algorithm 138, a computervision system 140, a navigation/pathing system 142, and/or an obstacleavoidance system 144, etc.

The steering unit 132 is operable to adjust the heading of vehicle 100.For example, the steering unit can adjust the axis (or axes) of one ormore of the wheels/tires 121 so as to effect turning of the vehicle. Thethrottle 134 is configured to control, for instance, the operating speedof the engine/motor 118 and, in turn, adjust forward acceleration of thevehicle 100 via the transmission 120 and wheels/tires 121. The brakeunit 136 decelerates the vehicle 100. The brake unit 136 can usefriction to slow the wheels/tires 121. In some embodiments, the brakeunit 136 inductively decelerates the wheels/tires 121 by a regenerativebraking process to convert kinetic energy of the wheels/tires 121 toelectric current.

The sensor fusion algorithm 138 is an algorithm (or a computer programproduct storing an algorithm) configured to accept data from the sensorsystem 104 as an input. The data may include, for example, datarepresenting information sensed at the sensors of the sensor system 104.The sensor fusion algorithm 138 can include, for example, a Kalmanfilter, Bayesian network, etc. The sensor fusion algorithm 138 providesassessments regarding the environment surrounding the vehicle based onthe data from sensor system 104. In some embodiments, the assessmentscan include evaluations of individual objects and/or features in theenvironment surrounding vehicle 100, evaluations of particularsituations, and/or evaluations of possible interference between thevehicle 100 and features in the environment (e.g., such as predictingcollisions and/or impacts) based on the particular situations.

The computer vision system 140 can process and analyze images capturedby camera 130 to identify objects and/or features in the environmentsurrounding vehicle 100. The detected features/objects can includetraffic signals, road way boundaries, other vehicles, pedestrians,and/or obstacles, etc. The computer vision system 140 can optionallyemploy an object recognition algorithm, a Structure From Motion (SFM)algorithm, video tracking, and/or available computer vision techniquesto effect categorization and/or identification of detectedfeatures/objects. In some embodiments, the computer vision system 140can be additionally configured to map the environment, track perceivedobjects, estimate the speed of objects, etc.

The navigation and pathing system 142 is configured to determine adriving path for the vehicle 100. For example, the navigation andpathing system 142 can determine a series of speeds and directionalheadings to effect movement of the vehicle along a path thatsubstantially avoids perceived obstacles while generally advancing thevehicle along a roadway-based path leading to an ultimate destination,which can be set according to user inputs via the user interface 116,for example. The navigation and pathing system 142 can additionally beconfigured to update the driving path dynamically while the vehicle 100is in operation on the basis of perceived obstacles, traffic patterns,weather/road conditions, etc. In some embodiments, the navigation andpathing system 142 can be configured to incorporate data from the sensorfusion algorithm 138, the GPS 122, and one or more predetermined maps soas to determine the driving path for vehicle 100.

The obstacle avoidance system 144 can represent a control systemconfigured to identify, evaluate, and avoid or otherwise negotiatepotential obstacles in the environment surrounding the vehicle 100. Forexample, the obstacle avoidance system 144 can effect changes in thenavigation of the vehicle by operating one or more subsystems in thecontrol system 106 to undertake swerving maneuvers, turning maneuvers,braking maneuvers, etc. In some embodiments, the obstacle avoidancesystem 144 is configured to automatically determine feasible(“available”) obstacle avoidance maneuvers on the basis of surroundingtraffic patterns, road conditions, etc. For example, the obstacleavoidance system 144 can be configured such that a swerving maneuver isnot undertaken when other sensor systems detect vehicles, constructionbarriers, other obstacles, etc. in the region adjacent the vehicle thatwould be swerved into. In some embodiments, the obstacle avoidancesystem 144 can automatically select the maneuver that is both availableand maximizes safety of occupants of the vehicle. For example, theobstacle avoidance system 144 can select an avoidance maneuver predictedto cause the least amount of acceleration in a passenger cabin of thevehicle 100.

The vehicle 100 also includes peripherals 108 configured to allowinteraction between the vehicle 100 and external sensors, othervehicles, other computer systems, and/or a user, such as an occupant ofthe vehicle 100. For example, the peripherals 108 for receivinginformation from occupants, external systems, etc. can include awireless communication system 146, a touchscreen 148, a microphone 150,and/or a speaker 152.

In some embodiments, the peripherals 108 function to receive inputs fora user of the vehicle 100 to interact with the user interface 116. Tothis end, the touchscreen 148 can both provide information to a user ofvehicle 100, and convey information from the user indicated via thetouchscreen 148 to the user interface 116. The touchscreen 148 can beconfigured to sense both touch positions and touch gestures from auser's finger (or stylus, etc.) via capacitive sensing, resistancesensing, optical sensing, a surface acoustic wave process, etc. Thetouchscreen 148 can be capable of sensing finger movement in a directionparallel or planar to the touchscreen surface, in a direction normal tothe touchscreen surface, or both, and may also be capable of sensing alevel of pressure applied to the touchscreen surface. An occupant of thevehicle 100 can also utilize a voice command interface. For example, themicrophone 150 can be configured to receive audio (e.g., a voice commandor other audio input) from a user of the vehicle 100. Similarly, thespeakers 152 can be configured to output audio to the user of thevehicle 100.

In some embodiments, the peripherals 108 function to allow communicationbetween the vehicle 100 and external systems, such as devices, sensors,other vehicles, etc. within its surrounding environment and/orcontrollers, servers, etc., physically located far from the vehicle thatprovide useful information regarding the vehicle's surroundings, such astraffic information, weather information, etc. For example, the wirelesscommunication system 146 can wirelessly communicate with one or moredevices directly or via a communication network. The wirelesscommunication system 146 can optionally use 3G cellular communication,such as CDMA, EVDO, GSM/GPRS, and/or 4G cellular communication, such asWiMAX or LTE. Additionally or alternatively, wireless communicationsystem 146 can communicate with a wireless local area network (WLAN),for example, using WiFi. In some embodiments, wireless communicationsystem 146 could communicate directly with a device, for example, usingan infrared link, Bluetooth, and/or ZigBee. The wireless communicationsystem 146 can include one or more dedicated short range communication(DSRC) devices that can include public and/or private datacommunications between vehicles and/or roadside stations. Other wirelessprotocols for sending and receiving information embedded in signals,such as various vehicular communication systems, can also be employed bythe wireless communication system 146 within the context of the presentdisclosure.

As noted above, the power supply 110 can provide power to components ofvehicle 100, such as electronics in the peripherals 108, computer system112, sensor system 104, etc. The power supply 110 can include arechargeable lithium-ion or lead-acid battery for storing anddischarging electrical energy to the various powered components, forexample. In some embodiments, one or more banks of batteries can beconfigured to provide electrical power. In some embodiments, the powersupply 110 and energy source 119 can be implemented together, as in someall-electric cars.

Many or all of the functions of vehicle 100 can be controlled viacomputer system 112 that receives inputs from the sensor system 104,peripherals 108, etc., and communicates appropriate control signals tothe propulsion system 102, control system 106, peripherals, etc. toeffect automatic operation of the vehicle 100 based on its surroundings.Computer system 112 includes at least one processor 113 (which caninclude at least one microprocessor) that executes instructions 115stored in a non-transitory computer readable medium, such as the datastorage 114. The computer system 112 may also represent a plurality ofcomputing devices that serve to control individual components orsubsystems of the vehicle 100 in a distributed fashion.

In some embodiments, data storage 114 contains instructions 115 (e.g.,program logic) executable by the processor 113 to execute variousfunctions of vehicle 100, including those described above in connectionwith FIG. 1. Data storage 114 may contain additional instructions aswell, including instructions to transmit data to, receive data from,interact with, and/or control one or more of the propulsion system 102,the sensor system 104, the control system 106, and the peripherals 108.

In addition to the instructions 115, the data storage 114 may store datasuch as roadway maps, path information, among other information. Suchinformation may be used by vehicle 100 and computer system 112 duringoperation of the vehicle 100 in the autonomous, semi-autonomous, and/ormanual modes to select available roadways to an ultimate destination,interpret information from the sensor system 104, etc.

The vehicle 100, and associated computer system 112, providesinformation to and/or receives input from, a user of vehicle 100, suchas an occupant in a passenger cabin of the vehicle 100. The userinterface 116 can accordingly include one or more input/output deviceswithin the set of peripherals 108, such as the wireless communicationsystem 146, the touchscreen 148, the microphone 150, and/or the speaker152 to allow communication between the computer system 112 and a vehicleoccupant.

The computer system 112 controls the operation of the vehicle 100 basedon inputs received from various subsystems indicating vehicle and/orenvironmental conditions (e.g., propulsion system 102, sensor system104, and/or control system 106), as well as inputs from the userinterface 116, indicating user preferences. For example, the computersystem 112 can utilize input from the control system 106 to control thesteering unit 132 to avoid an obstacle detected by the sensor system 104and the obstacle avoidance system 144. The computer system 112 can beconfigured to control many aspects of the vehicle 100 and itssubsystems. Generally, however, provisions are made for manuallyoverriding automated controller-driven operation, such as in the eventof an emergency, or merely in response to a user-activated override,etc.

The components of vehicle 100 described herein can be configured to workin an interconnected fashion with other components within or outsidetheir respective systems. For example, the camera 130 can capture aplurality of images that represent information about an environment ofthe vehicle 100 while operating in an autonomous mode. The environmentmay include other vehicles, traffic lights, traffic signs, road markers,pedestrians, etc. The computer vision system 140 can categorize and/orrecognize various aspects in the environment in concert with the sensorfusion algorithm 138, the computer system 112, etc. based on objectrecognition models pre-stored in data storage 114, and/or by othertechniques.

Although the vehicle 100 is described and shown in FIG. 1 as havingvarious components of vehicle 100, e.g., wireless communication system146, computer system 112, data storage 114, and user interface 116,integrated into the vehicle 100, one or more of these components canoptionally be mounted or associated separately from the vehicle 100. Forexample, data storage 114 can exist, in part or in full, separate fromthe vehicle 100, such as in a cloud-based server, for example. Thus, oneor more of the functional elements of the vehicle 100 can be implementedin the form of device elements located separately or together. Thefunctional device elements that make up vehicle 100 can generally becommunicatively coupled together in a wired and/or wireless fashion.

FIG. 2 shows an example vehicle 200 that can include some or all of thefunctions described in connection with vehicle 100 in reference toFIG. 1. Although vehicle 200 is illustrated in FIG. 2 as a four-wheelsedan-type car for illustrative purposes, the present disclosure is notso limited. For instance, the vehicle 200 can represent a truck, a van,a semi-trailer truck, a motorcycle, a golf cart, an off-road vehicle, ora farm vehicle, etc.

The example vehicle 200 includes a sensor unit 202, a wirelesscommunication system 204, a RADAR unit 206, a laser rangefinder unit208, and a camera 210. Furthermore, the example vehicle 200 can includeany of the components described in connection with vehicle 100 ofFIG. 1. The RADAR unit 206 and/or laser rangefinder unit 208 canactively scan the surrounding environment for the presence of potentialobstacles and can be similar to the RADAR unit 126 and/or laserrangefinder/LIDAR unit 128 in the vehicle 100.

The sensor unit 202 is mounted atop the vehicle 200 and includes one ormore sensors configured to detect information about an environmentsurrounding the vehicle 200, and output indications of the information.For example, sensor unit 202 can include any combination of cameras,RADARs, LIDARs, range finders, and acoustic sensors. The sensor unit 202can include one or more movable mounts that could be operable to adjustthe orientation of one or more sensors in the sensor unit 202. In oneembodiment, the movable mount could include a rotating platform thatcould scan sensors so as to obtain information from each directionaround the vehicle 200. In another embodiment, the movable mount of thesensor unit 202 could be moveable in a scanning fashion within aparticular range of angles and/or azimuths. The sensor unit 202 could bemounted atop the roof of a car, for instance, however other mountinglocations are possible. Additionally, the sensors of sensor unit 202could be distributed in different locations and need not be collocatedin a single location. Some possible sensor types and mounting locationsinclude RADAR unit 206 and laser rangefinder unit 208. Furthermore, eachsensor of sensor unit 202 can be configured to be moved or scannedindependently of other sensors of sensor unit 202.

In an example configuration, one or more RADAR scanners (e.g., the RADARunit 206) can be located near the front of the vehicle 200, to activelyscan the region in front of the car 200 for the presence ofradio-reflective objects. A RADAR scanner can be situated, for example,in a location suitable to illuminate a region including a forward-movingpath of the vehicle 200 without occlusion by other features of thevehicle 200. For example, a RADAR scanner can be situated to be embeddedand/or mounted in or near the front bumper, front headlights, cowl,and/or hood, etc. Furthermore, one or more additional RADAR scanningdevices can be located to actively scan the side and/or rear of thevehicle 200 for the presence of radio-reflective objects, such as byincluding such devices in or near the rear bumper, side panels, rockerpanels, and/or undercarriage, etc.

The wireless communication system 204 could be located on a roof of thevehicle 200 as depicted in FIG. 2. Alternatively, the wirelesscommunication system 204 could be located, fully or in part, elsewhere.The wireless communication system 204 may include wireless transmittersand receivers that could be configured to communicate with devicesexternal or internal to the vehicle 200. Specifically, the wirelesscommunication system 204 could include transceivers configured tocommunicate with other vehicles and/or computing devices, for instance,in a vehicular communication system or a roadway station. Examples ofsuch vehicular communication systems include dedicated short rangecommunications (DSRC), radio frequency identification (RFID), and otherproposed communication standards directed towards intelligent transportsystems.

The camera 210 can be a photo-sensitive instrument, such as a stillcamera, a video camera, etc., that is configured to capture a pluralityof images of the environment of the vehicle 200. To this end, the camera210 can be configured to detect visible light, and can additionally oralternatively be configured to detect light from other portions of thespectrum, such as infrared or ultraviolet light. The camera 210 can be atwo-dimensional detector, and can optionally have a three-dimensionalspatial range of sensitivity. In some embodiments, the camera 210 caninclude, for example, a range detector configured to generate atwo-dimensional image indicating distance from the camera 210 to anumber of points in the environment. To this end, the camera 210 may useone or more range detecting techniques.

For example, the camera 210 can provide range information by using astructured light technique in which the vehicle 200 illuminates anobject in the environment with a predetermined light pattern, such as agrid or checkerboard pattern and uses the camera 210 to detect areflection of the predetermined light pattern from environmentalsurroundings. Based on distortions in the reflected light pattern, thevehicle 200 can determine the distance to the points on the object. Thepredetermined light pattern may comprise infrared light, or radiation atother suitable wavelengths for such measurements.

The camera 210 can be mounted inside a front windshield of the vehicle200. Specifically, the camera 210 can be situated to capture images froma forward-looking view with respect to the orientation of the vehicle200. Other mounting locations and viewing angles of camera 210 can alsobe used, either inside or outside the vehicle 200.

The camera 210 can have associated optics operable to provide anadjustable field of view. Further, the camera 210 can be mounted tovehicle 200 with a movable mount to vary a pointing angle of the camera210, such as via a pan/tilt mechanism.

FIG. 3 is a block diagram of an example LIDAR device 300. The LIDARdevice 300 includes a light source 310, beam-steering optics 312, alight sensor 314, and a controller 316. The light source 310 may emitpulses of light toward the beam-steering optics 312, which directs thepulses of light 304 across a scanning zone 302. Reflective features inthe scanning zone 302 reflect the pulses of light 304 and the reflectedlight signals 306 can be detected by the light sensor 314. Thecontroller 316 regulates the operation of the light source 310 andbeam-steering optics 312 to scan pulses of light 304 across the scanningzone 302. The controller 316 can also be configured to estimatepositions of reflective features in the scanning zone 302 based on thereflected signals 306 detected by the light sensor 314. For example, thecontroller 316 can measure the time delay between emission of a pulse oflight and reception of a reflected light signal and determine thedistance to the reflective feature based on the time of flight of around trip to the reflective feature. In addition, the controller 316may use the orientation of the beam-steering optics 312 at the time thepulse of light is emitted to estimate a direction toward the reflectivefeature. For example, an orientation feedback system 318 can sendinformation to the controller 316 indicating the orientation of thebeam-steering optics 312 (and thus the direction of the emitted pulse oflight). The estimated direction (e.g., from the orientation feedbacksystem 318) and estimated distance (e.g., based on a measured timedelay) can be combined to estimate a three-dimensional position fromwhich the returning light signal 306 was reflected. The controller 316may combine a series of three-dimensional position estimations (e.g.,from each received reflected light signal 306) from across the scanningzone 302 to generate a three-dimensional point map 320 of reflectivefeatures in the scanning zone 302.

The light source 310 can be a laser light source that emits light in thevisible, infrared, and/or ultraviolet spectrum. Moreover, the lightsource 310 can optionally include a plurality of light sources eachemitting pulses of light. In an example with multiple light sources,each light source may be directed to the scanning zone 302 by thebeam-steering optics 312. For example, a group of light sources can eachbe aimed at a single rotating mirror. The group of light sources can beaimed such that each light source reflects from the mirror at a distinctangle and therefore scans a substantially distinct region of thescanning zone 302. Additionally or alternatively, the light sources mayscan wholly or partially overlapping regions of the scanning zone 302.Additionally or alternatively, more than one beam-steering opticaldevice can be provided, and each such beam-steering optical device candirect light pulses from one or more light sources.

As illustrated in FIG. 3, the reflected light signals may be directed tothe light sensor 314 by the beam-steering optics 312. However, this isjust one configuration provided for example purposes. Some embodimentsof the LIDAR device 300 may be arranged with a light sensor configuredto receive reflected light from the scanning zone 302 without firstbeing directed via the beam-steering optics 312.

The controller 316 is configured to control the operation of the lightsource 310 and the beam-steering optics 312 to cause pulses of light 304to be emitted across the scanning zone 302. The controller 316 alsoreceives information from the light sensor 314 to indicate the receptionof reflected light signals 306 at the light sensor 314. The controller316 can then determine the distance to surrounding objects bydetermining the time delay between emission of a light pulse andreception of a corresponding reflected light signal. The time delayindicates the round trip travel time of the emitted light from the LIDARdevice 300 and a reflective feature in the scanning zone 302. Thus, adistance to a reflective feature may be estimated by dividing the timedelay by the speed of light, for example.

The three-dimensional position of the reflective feature can then beestimated by combining the estimated distance with the orientation ofthe beam-steering optics 312 during the emission of the pulse. In someexamples, the orientation of the beam-steering optics 312 can bedetected by an orientation feedback system 318 configured to sense theorientation of the beam-steering optics 312. The orientation feedbacksystem 318 can then provide an indication of the orientation of thebeam-steering optics 312 to the controller 316 and use the orientationinformation to estimate three-dimensional positions associated withreceived reflected light signals.

In some examples, by scanning the emitted pulses 304 across the scanningzone 302, the LIDAR device 300 can be used to locate reflective featuresin the scanning zone 302. Each reflected light signal received at thelight sensor 314 may be associated with a three-dimensional point inspace based on the measured time delay and orientation of thebeam-steering optics 312 associated with each reflected light signal.The combined group of three-dimensional points following a scan of thescanning zone 302 can be combined together to create a 3-D point map320, which may be output from the LIDAR device 300. The 3-D point map320 may then be analyzed by one or more functional modules used tocontrol an autonomous vehicle. For example, the 3-D point map 320 may beused by the obstacle avoidance system 144 and/or navigation/pathingsystem 142 in the vehicle 100 to identify obstacles surrounding thevehicle 100 and/or to control the vehicle 100 to avoid interference withsuch obstacles.

The beam-steering optics 312 may include one or more mirrors, lenses,filters, prisms, etc., configured to direct light pulses from the lightsource 310 to the scanning zone 302. The beam-steering optics 312 may beconfigured to direct the light pulses according to an orientationindicated by signals from the controller 316. For example, thebeam-steering optics 312 may include one or more mirrors configured torotate and/or oscillate according to signals from the controller 316.The controller 316 can thereby control the direction of emission oflight pulse(s) 304 from the LIDAR device 300 by providing suitablecontrol signals to the beam-steering optics 312.

The beam-steering optics 312 can be operated to scan the light from thelight source 310 across the scanning zone 302 at a regular interval(e.g., to complete a full scan of the scanning zone 302 periodically).In this way, the LIDAR device 300 may be used to dynamically generatethree-dimensional point maps of reflecting features in the scanning zone302. The three-dimensional map may be updated at a frequency that issufficient to provide information useful for real time navigation and/orobstacle avoidance for an autonomous vehicle (e.g., the autonomousvehicles 100, 200 discussed above in connection with FIGS. 1-2). Forexample, the 3-D point map 320 may be refreshed at a frequency of about10 hertz to about 100 hertz and such refreshed point map information maybe used to identify obstacles of an autonomous vehicle on which theLIDAR device 300 is mounted and then control the vehicle to avoidinterference with such obstacles.

FIG. 4A is a diagram of an example LIDAR system 400 that scans ascanning zone 430 via an oscillating mirror 420. The example LIDARsystem 400 includes a light source 410 arranged to emit pulses of lightat a reflective surface 424 of the oscillating mirror 420. The LIDARsystem 400 may also include a light sensor (not shown), orientationfeedback system (not shown), and controller (not shown), similar tothose described above in connection with FIG. 3. Thus, the LIDAR system400 illustrated in FIG. 4 may be configured to detect returningreflected light signals and use the reflected light signals to generatethree-dimensional point map of reflective features in the scanning zone430.

The oscillating mirror 420 can rotate about its axis 422. The axis 422may be defined by, for example, a pivot rod oriented parallel to thereflective surface 424 of the mirror 420. The oscillating mirror 420 canbe driven to oscillate back and forth (as indicated by the motion arrow426) such that the light from the light source 410 sweeps across anangle θ. The scanning zone 430 may therefore be a region defined by acone having an apex approximately located at the oscillating mirror 420and with opening angle θ. For example, the mirror 420 may be driven tooscillate with a frequency of about 60 hertz, which may also be therefresh rate of the LIDAR system 400.

FIG. 4B is a diagram of an example LIDAR system 440 with multiple lightsources 452-456 each scanning a portion of a scanning zone. For examplepurposes FIG. 4B shows the system 440 with three light sources (i.e.,the first light source 452, second light source 454, and third lightsource 456). The light sources 452-456 can be arranged such that lightemitted from each is directed toward a reflective side 464 of anoscillating mirror 460. The light sources 452-456 can each emit lightfrom a distinct position such that pulses of light emitted from each ofthe respective light sources 452-456 define an angle with respect to oneanother. For example, the first light source 452 and second light source454 can emit light from distinct positions that are separated by anangle θ when the light emitted from each is aimed at the oscillatingmirror 460. Similarly, the second light source 454 and third lightsource 456 can be arranged such that light emitted from the two lightsources 454, 456 defines an angle θ when the light emitted from each isaimed at the oscillating mirror 460. Thus, by steering light emittedfrom each light source (e.g., the light sources 452-456), theoscillating mirror 460 can scan each light source across a respectivescanning zone (e.g., the scanning zones 472-476). The angular span ofeach scanning zone 472-476 (e.g., the angle θ′ shown in FIG. 4B) can bedue to the oscillation of the mirror 460 (e.g., as shown by thedirectional arrow 466). Accordingly, the angular span of each scanningzone may be the same (e.g., θ′). Alternatively, the respective angularspans of the scanning zones may be different in some examples.

The angular separation between the light sources 452-456 may cause theemitted light pulses from each light source to scan across a distinctscanning zone. Thus, each of the light sources 452-456 can be associatedwith a distinct scanning zone. For example, the first light source 452can be scanned across the first scanning zone 472; the second lightsource 454 can be scanned across the second scanning zone 474; and thethird light source 456 can be scanned across the third scanning zone476. Additionally or alternatively, the scanning zones (e.g., thescanning zones 472-476) may include at least partially overlappingregions of surrounding environment. The scanning zones 472-476 areidentified separately for convenience in explaining the arrangement withmultiple angularly offset light sources. However, it is noted thatinformation from the multiple scanning zones can be combined (e.g., viaa controller) to create a combined three-dimensional point map for useby navigation and/or obstacle avoidance systems of an autonomous vehicle(e.g., the autonomous vehicles 100, 200 described in connection withFIGS. 1 and 2 above).

The LIDAR system 440 is shown with three light sources (e.g., the lightsources 452-456) each directed at a single oscillating mirror 460 toscan three scanning zones (e.g., the scanning zones 472-476). However,some embodiments of the present disclosure may include more than threelight sources and more than three scanning zones. For example, ten lightsources may be arranged to be with approximately 2° of relative angularseparation (or another relative angular separation), such that eachlight source scans a scanning zone that is offset from its neighbor byapproximately 2°. The oscillating mirror 460 may oscillate to cause thelight from each light source to scan a region with an opening angle ofapproximately 2°. For example, the oscillating mirror 460 may oscillateback and forth by 2° (e.g., plus and minus 1° from a nominal position)such that the pulses of light from the light sources are scanned acrosstheir respective scanning zones.

FIG. 5A is an aspect view of an example beam-steering device having anarrangement of multiple mirrors. As described further below, themultiple mirrors can be driven to oscillate such that a pulse of lightincident on the beam-steering device (e.g., from light source in a LIDARsystem) can be directed toward a scanning zone according to theorientation of the mirrors. The arrangement of multiple mirrors caninclude reflective slats arranged with respective axes of rotation ofthe reflective slats oriented in parallel. Each of the reflective slatscan be separately controlled by an electromagnetic driving system thatcauses the reflective slats to oscillate in phase while accounting forvariations in resonant frequencies of each reflective slat. By operatingthe reflective slats to oscillate in phase, the reflective slats aresubstantially aligned in parallel planes at any given instant, and solight incident on the slats can be reflected in a common direction. Anincident light pulse (or series of pulses) can then be simultaneouslyreflected by multiple ones of the reflective slats in the arrangementwith the reflected light from each slat directed in a common direction.The arrangement of reflective slats described herein in connection withFIGS. 5-6 is thus one example of a beam-steering device with multiplemirrors driven in phase to cooperatively scan pulses of light across ascanning zone for a LIDAR device.

The example beam-steering device shown in FIG. 5A illustrates a firstreflective slat 520 and a second reflective slat 530 for convenience inexplanation, although some embodiments may include additional reflectiveslats (such as the third reflective slat partially visible in FIG. 5A).Moreover, the diagrams of the beam-steering device and reflective slatsare not necessarily illustrated to scale in FIGS. 5-6. Instead, thevarious features of the example beam-steering device are illustrated forexplanatory purposes in a manner intended to facilitate understandingand may exaggerate certain features and/or dimensions.

The example beam-steering device shown in FIG. 5A includes a frame 510with a first side rail 511 and a second side rail 512. The firstreflective slat 520 is connected to the frame 510 by a connecting arm524 connected to the first side rail 511 and a connecting arm 522connected to the second side rail 512. The connecting arms 522, 524 canconnect to the reflective slat 520 along a line that defines the axis ofrotation of the reflective slat 520. During rotation of the reflectiveslat 520 with respect to the frame 510, the connecting arms 522, 524 maytwist (e.g., torsionally deform) such that the normal direction of thereflective slat 520 rotates about an axis of rotation that passesthrough the two connecting arms 522, 524. In some examples, theconnecting arms 522, 524 may resist twisting, and thereby bias thereflective slat 520 in a nominal position where the connecting arms 522,524 are in a relaxed untwisted state. The connecting arms 522, 524 maytherefore generate a restorative force that urges the reflective slat520 toward its nominal position in a manner analogous to a mass on aspring that is urged toward a position where the spring is in a relaxedstate. Perturbing the reflective slat 520 can therefore cause thereflective slat 520 to oscillate about its nominal position. Further,applying periodic perturbations to the reflective slat 520 can cause thereflective slat 520 to undergo oscillatory motion with a frequency basedon the frequency of the applied perturbations.

The connecting arms 522, 524 can be arranged such that the axis ofrotation of the reflective slat 520 approximately bisects the reflectiveslat 520. For example, the connecting arms 522, 524 may connect to thereflective slat 520 at mid-points of opposing ends of the reflectiveslat 520 such that the axis of rotation defined by the connecting arms522, 524 approximately bisects the reflective slat 520. In someexamples, the reflective slat 520 can have an elongated shape with along dimension aligned in parallel to the axis of rotation. Thus, theconnecting arms 522, 524 may connect to the reflective slat 520 alongsides extending in the width dimension of the reflective slat 520 (e.g.,to short sides of the rectangle-shaped reflective slat 520). At the sametime, the side edges 526, 528 along the length dimension of thereflective slat 520 may be free of connection to the connecting arms522, 524. In an example where a pattern of reflective slats are arrangedin a single row with each slat having an approximately rectangle shape,the long sides of the slats can be situated next to one another and theaxes of rotation of the slats can be oriented in parallel and along thelengths of the slats.

The connecting arms 522, 524 may connect to the reflective slat 520 atmid-points of opposite ends of the reflective slat 520. The connectingarms 522, 524 may be, for example, narrow strips integrally formed withthe reflective slat 520. For example, the connecting arms 522, 524 maybe integrally formed with the reflective slat 520. Additionally oralternatively, the connecting arms 522, 524 may be integrally formedwith the side rails 511, 512 (or some portion of the side rails).Additionally or alternatively, the connecting arms may mechanicallyconnect to one or both of the reflective slat 520 and the side rails511, 512 using adhesives, fasteners, welding, soldering, etc.

In some embodiments, the connecting arms 522, 524 may be narrow stripsthat are integrally formed with the reflective slat 520. For example,the reflective slat 520 and the connecting arms 522, 524 can be formedby cutting out the shape of the reflective slat 520 and connecting arms522, 524 from a sheet of suitably reflective flexible material, such asa sheet of silicone steel. Moreover, a pattern of one or more suchmirrors arranged in a pattern of reflective slats suspended byintegrally formed connecting arms may be cut out from a sheet ofsilicone steel using a high pressure water-jet cutting system, forexample.

Similar to the first reflective slat 520, the second reflective slat 530is mounted to the frame 510 by connecting arms 532, 534. The connectingarms 532, 534 can twist to allow the second reflective slat 530 torotate with respect to the frame 510. Thus, the second reflective slat530 can rotate about an axis of rotation defined by the two connectingarms 532, 534 (e.g., an axis of rotation that passes through theconnecting arms 532, 534). The two connecting arms 532, 534 may be, forexample, narrow strips of material that are integrally formed with thesecond reflective slat 530.

The reflective slat 530 may have an elongated shape (e.g., a rectangle),and connecting arms 532, 534 can be connected to opposite ends of thereflective slat 530 along the short sides of the reflective slat 530.The sides 536, 538 along the long dimension of the reflective slat 530can be situated adjacent neighboring reflective slats in the pattern.For example, the long side 536 of the reflective slat 530 can beadjacent the long side 528 of the reflective slat 520, and the two canedges can be separated by a distance sufficient to allow each reflectiveslat to oscillate about its respective axis of rotation withoutinterfering with the other reflective slat.

The axes of rotation of the two reflective slats 520, 530 can beoriented in parallel. Moreover, the axes of rotation of the tworeflective slats 520, 530 (and any additional reflective slats in thebeam-steering device) can be oriented in parallel and in a common plane,such as the plane of the frame 510. During oscillation of the pattern ofreflective slats, the respective long edges (e.g., the edges 526, 528,536, 538) of the reflective slats can oscillate up and down, through thecommon plane of the axes of rotation, while the axes of rotation remainin the common plane.

A substrate 540 including an electromagnetic driving system can bemounted to an underside of the frame 510 via first and second legs 514,516 of the frame 510. That is, the legs 514, 516 can act as spacers tocreate a separation between the substrate 540 and the bottom side of thepattern of oscillating mirrors (e.g., the pattern of reflective slats).The electromagnetic driving system can include pairs of electromagnetsarranged to attract particular ones of the reflective slats. Forexample, a first pair of electromagnets 542 and a second pair ofelectromagnets 544 are situated on the substrate 540 underneath thefirst reflective slat 520. The electromagnets 542, 544 can include, forexample ferromagnetic pegs extending outward from the substrate 540toward the underside of the reflective slat 520. The pegs can extendinto the substrate 540 where conductive traces coil around the pegs suchthat the pegs are cores in the electromagnets. Energizing the coils inthe substrate 540 with current activates the electromagnets 542, 544 andthereby attracts the reflective slat 520 toward the electromagnets 542,544. For example, where the reflective slat 520 includes silicone steel,energizing the electromagnets 542, 544 induces a complementary magneticresponse in the reflective slat 520 via surface currents in the siliconesteel. However, it is noted that silicone steel is only one example andother materials may be used for the reflective slats, such as othermetals, etc. that exhibit: sufficient induced magnetization to allow forcontrolling with an electromagnetic driving system, sufficientflexibility to allow for oscillating the reflective slats, and/orsufficient reflectivity to allow for reflecting incident light.Moreover, combinations of materials that exhibit such properties mayalso be used to form the reflective slats, such as a multi-layercomposite that includes a ferromagnetic bottom later, a reflective topcoating, and/or fiber-based flexible ends to allow torsionaloscillation.

In some embodiments, each pair of electromagnets (e.g., the pair ofelectromagnets 542), can be arranged to have opposite polarity. Forexample the conductive traces that coil around the pegs can be wound inopposite directions such that each pair of electromagnets includes, whenenergized: one electromagnet with its north pole faced toward theunderside of the reflective slat 520, and one electromagnet with itssouth pole faced toward the underside of the reflective slat 520. Thisarrangement can allow for the respective pairs of electromagnets and theinduced magnetic response of the reflective slat 520 to complete amagnetic circuit in an area roughly proportionate to the spacing of eachpair of electromagnets (e.g., the pair of electromagnets 542). Providingpairs of opposite-polarity electromagnets can thus substantially confineinduced magnetic responses in the reflective slat 520 to the region neareach pair of electromagnets and thereby avoid substantial inducedmagnetic effects across the remainder of the reflective slat.

Situating the pairs of electromagnets 542, 544 on the substrate 540 at aposition radially offset from the axis of rotation of the reflectiveslat 520 (e.g., with ends of the pegs proximate the long edge 526 of thereflective slat 520) allows for torque to be applied on the reflectiveslat 520. For example, energizing the electromagnets 542, 544 canattract the long edge 526 of the reflective slat 520 toward theelectromagnets 542, 544 and thereby urge the reflective slat 520 torotate about its axis defined by the connecting arms 522, 524.Activating the electromagnets 542, 544 can thereby urge the long edge526 toward the substrate 540 while the opposing long edge 528 moves awayfrom the substrate 540.

Following the attraction of the long edge 526 of the reflective slat 520toward the substrate 540, the electromagnets 542, 544 can bedeactivated. For example, current flowing through the traces coiledaround the pegs of the electromagnets 542, 544 can be turned off. Oncethe electromagnets 542, 544, the reflective slat 520 can rotate backtoward its nominal position. For example, the connecting arms 522, 524,which twist to allow the reflective slat 520 to rotate, can urge thereflective slat 520 to move back toward its nominal position (e.g.,where the connecting arms 522, 524 are in an untwisted, relaxed state).In some examples, the twisted connecting arms 522, 524 can cause thereflective slat 520 to oscillate about its axis of rotation followingdeactivation of the electromagnets 542, 544. For example, once theelectromagnetic attractive force ceases, the reflective slat 520 mayswing in the opposite direction of rotation until the long edge 528 isrelatively closer to the substrate 540 than the edge 526 that wasinitially attracted by the electromagnets 542, 544. The twisting of theconnecting arms 522, 524 can thereby serve as a restorative force on theorientation of the reflective slat that continuously urges thereflective slat 520 toward its nominal position and with the magnitudeof the restorative related to the amount of twisting in the connectingarms 522, 524 (and thus the angular change away from the nominalposition). In some embodiments, the connecting arms 522, 524 cause thereflective slat 520 to rotate back and forth about its axis of rotationin an oscillatory manner following a perturbation away from its nominalposition due to the electromagnets 542, 544.

Similarly, the second reflective slat 530 can be caused to oscillateabout its axis of rotation by the electromagnets 546, 548. Theelectromagnets 546, 548 can be activated to induce a magnetic attractiveforce between the electromagnets 546, 548 and the reflective slat 530.Because the electromagnets 546, 548 are offset from the axis of rotationof the reflective slat 530, the attractive force exerts a torque on thereflective slat 530 and thereby causes the second reflective slat 530 torotate about the axis defined by the connecting arms 532, 534. Theattractive force can result in, for example, the long edge 536 of thesecond reflective slat 530 being urged toward the electromagnets 546,548 (and thus the substrate 540) while the opposite long edge 538 movesaway from the substrate 530. Deactivating the electromagnets 546, 548(e.g., by halting current through traces wrapped around the pegs in theelectromagnets 546, 548) ceases the induced magnetism and the secondreflective slat 530 can then rotate back toward its nominal position toallow the connecting arms 532, 534 to untwist.

For example, the reflective slats 520, 530 can be driven with anelectromagnetic driving system to oscillate in phase such that theorientation of the reflective slats (e.g., defined by the normaldirections of the reflective slats) can be in parallel. An incidentlight pulse can have a beam size that spans more than one of thereflective slats, and thus each reflective slat can separately reflect aportion of the incident light in a common direction. The arrangement ofseparately controlled reflective slats can be used to direct (“steer”)incident light (e.g., according to substantially plane-parallelorientation of each reflective slat). By operating the pattern ofreflective slats (e.g., the reflective slats 520, 530, etc.) tooscillate in phase, reflected light can be scanned across a scanningzone according to the frequency of the oscillation.

FIG. 5B is a top view of the example beam-steering device shown in FIG.5A. FIG. 5C is an end view of the example beam-steering device shown inFIG. 5A. FIGS. 5B and 5C identify several dimensions for convenience inreferring to the drawings, although it is noted that the diagrams inFIGS. 5B and 5C are not necessarily drawn to scale and therefore therelative lengths of the dimensions indicated in the drawings may notreflect relative relationships between the various dimensions.

With reference to both FIGS. 5B and 5C, the reflective slats 520, 530have an outward-facing reflective surface 521, 531 and an opposite backsurface 523, 533 (e.g., the surface facing the substrate 540). Thereflective surfaces 521, 531 can be coated with a reflective material,such as a layer of metal formed on the reflective slat 520. Thereflective surface 521, 523 may include, for example, aluminum, tin,gold, silver, combinations of these, etc. and may additionally oralternatively include a substantially transparent layer (e.g., glass,polymeric material, etc.) coated on the reflective material to preservethe reflective surface 521, 523. For example, a transparent protectivemay prevent the reflective layer from degrading by oxidation, surfacedeformation, etc.

The reflective slats 520, 530 each have a generally rectangular shapewith length L_(sl) and width W_(sl). In some embodiments, the reflectiveslats 520, 530 can each have a length of about 3 centimeters and a widthof about 0.5 centimeters, for example. The lengths of the reflectiveslats 520, 530 (along the long sides 526, 528, 536, 538) can extendparallel to the respective axes of rotation defined by the pairs ofconnecting arms 522, 524 and 532, 534 for each reflective slat. At thesame time, the widths of the reflective slats 520, 530 (along the shortsides 525, 527, 535, 537) can extend perpendicular to the respectiveaxes of rotation defined by the pairs of connecting arms 522, 524 and532, 534 for each reflective slat. Thus, the length dimension L_(sl) ofthe reflective slats extends between the opposite short ends 525 and 527(or 535 and 537), while the width dimension W_(sl) of the reflectiveslats extends between the opposite long ends 526 and 528 (or 536 and538).

The reflective slat 520 can be situated adjacent the second reflectiveslat 530. The two reflective slats 520, 530 can be separated by aseparation distance d_(sep) (labeled in FIG. 5B) between the long sideedges 528 and 536 of the two reflective slats 520, 530. The separationdistance d_(sep) can generally be selected to allow enough space for thetwo reflective slats 520, 530 to oscillate without interfering with oneanother. For example, the separation distance d_(sep) may be minimizedwhile accounting for the thickness of the slats 520, 530 and forengineering and/or manufacturing tolerances. Generally, minimizing theseparation distance d_(sep) between adjacent ones of the reflectiveslats (e.g., the slats 520, 530) allows the total combined reflectivesurface area of the array of oscillating mirrors to be maximized.Moreover, the two reflective slats 520, 530 can be arranged withsubstantially parallel axes of rotation (e.g., as defined by a linebetween the pairs of connecting arms 522, 524 or 532, 534) that are alsooriented in a common plane (e.g., the plane of the frame 510 to whichthe connecting arms 522, 524, 532, 534 are mounted).

The connecting arms 522, 524, 532, 534 each have a length L_(ax) andwidth W_(ax). Both the length L_(ax) and width W_(ax) of the connectingarms 522, 524 influence the resistance to twisting of the connectingarms 522, 524, and thus influence the susceptibility of the reflectiveslat 520 to oscillate in response to being acted on by theelectromagnets 542, 544. The connecting arms 522, 524, 532, 534 alsohave a thickness (as evident in FIG. 5C), which can influence theoscillatory response of the reflective slat 520. The thickness of theconnecting arms 522, 524, 532, 534 may be substantially the same as thethickness of the reflective slats 520, 530 (e.g., the distance betweenthe reflective surface 521 and the back surface 523). Moreover, thematerial used to form the connecting arms 522, 524 can influence thesusceptibility to twisting the connecting arms 522, 524. For example,relatively more flexible materials may exhibit less resistance totwisting than relatively less flexible materials. Similar to thereflective slat 520, the oscillatory responsiveness of the reflectiveslat 530 can be influenced by the dimensions and/or materials of theconnecting arms 532, 534.

In some embodiments, the orientation of the axes of rotation can beselected to provide a desired moment of inertia of the reflective slat520, 530. A desired moment of inertia may be selected, for example,based in part on a desired frequency of oscillation because relativelyhigher oscillation frequencies are more readily achievable by rotatingfeatures with relatively lower moments of inertia. For example, aligningthe axes of rotation along the lengths of the reflective slats 520, 530can provide a relatively lower moment of inertia, and therefore a higherachievable frequency of oscillation than in an arrangement with axes ofrotation aligned along the widths of the reflective slats 520, 530.

The connecting arms 522, 524, 532, 534 can be arranged to provide anaxis of rotation for each reflective slat 520, 530 that passes throughthe centers of mass of each of the reflective slats. For example, withreference to the reflective slat 520, the connecting arm 522 can connectat the midpoint of the short edge 525 and the connecting arm 524 canconnect at the midpoint of the short edge 527 such that the resultingaxis of rotation of the reflective slat 520 at least approximatelybisects the reflective slat 520 (e.g., along a line connecting themidpoints of the two short ends 525, 527). Similarly, the connectingarms 532, 534 can connect to the midpoints of the short edges 535, 537of the reflective slat 530 such that the resulting axis of rotation ofthe reflective slat 530 at least approximately bisects the reflectiveslat 530.

In some embodiments, a desired oscillatory response of the reflectiveslats 520, 530 (and any other reflective slats in the pattern of mirrorsof the beam-steering device) can be selected (“tuned”) by selecting thedimensions of the reflective slats and/or connecting arms (e.g., thedimensions L_(sl), W_(sl), L_(ax), W_(ax), etc.) the materials used toform the reflective slats and/or connecting arms, and/or the arrangementof the axes of rotation of the reflective slats.

FIGS. 5B and 5C also illustrate the electromagnets 542-548 of theelectromagnetic driving system used to cause the reflective slats 520,530 to oscillate. In particular, the end view of FIG. 5C shows that thepeg 544 a from one of the pair of electromagnets 544 emerges from thesubstrate 540 at a position that is radially offset from the axis ofrotation off the reflective slat 520. As shown in FIG. 5C, the peg 544 ais located on the substrate 540 at a radial distance d_(rad) from theposition of the axis of rotation of the reflective slat (e.g., asdefined by the center point of the connecting arm 522). Situating theelectromagnets 542, 544 to be radially offset from the axis of rotationby the distance d_(rad) (e.g., proximate the long side edge 526) allowsthe electromagnetic attraction between the electromagnets 542, 544 andthe reflective slat 520 to apply a torque on the reflective slat 520 andthereby cause the reflective slat 520 to oscillate about its axis ofrotation. At the same time, the distance d_(rad) is may be less than thehalf-width of the reflective slat 520, such that the electromagnets 542,544 are located entirely underneath the reflective slat 520 (and notalso underneath neighboring reflective slats). Situating theelectromagnets 542, 544 underneath only the reflective slat 520 alsoallows the induced magnetism of the reflective slat 520 to shieldneighboring magnetic slats (e.g., the reflective slat 530) from theeffects of the electromagnets 542, 544.

As shown in FIG. 5C, the end of the peg 544 a furthest from thesubstrate 540 is separated from the bottom side 523 of the reflectiveslat 520 by a distance d_(gap). The dimension d_(gap) can influence theamount of magnetic coupling between the reflective slat 520 and theelectromagnets 542, 544. The pairs of electromagnets 542, 544 fordriving the reflective slat 520 are described further with reference toFIG. 5D below.

FIG. 5D is a cross-sectional side view of one of the reflective slats520 that shows example electromagnets 542, 544 associated with thereflective slat 520. The first pair of electromagnets 542 includes afirst peg 542 a and a second peg 542 b that can be cores of the pair ofelectromagnets 542. The two pegs 542 a-b can each be magnetized byconductive traces embedded in the substrate 540 that coil around thepegs 542 a-b (e.g., the traces 566-568 coiled around the peg 542 a). Thetraces (e.g., the traces 566-568) can coil around pairs of pegs inopposite directions to create electromagnets with opposite polarity ineach pair of electromagnets. Thus, the traces 566-568 can coil aroundthe first peg 542 a in one direction and the traces around the secondpeg 542 b can coil in the opposite direction. As a result, theslat-facing end 562 of the first peg 542 a can have a north magneticpolarity while the opposite end 564 of the first peg 542 a has a southmagnetic polarity. At the same time, the slat-facing end of the secondpeg 542 b can have a south magnetic polarity while the opposite end ofthe second peg 542 b has a north magnetic polarity. Additionally oralternatively, the first peg 542 a can be energized with its southmagnetic polarity toward the reflective slat 520 and the second peg 542b can be simultaneously energized with its north magnetic polaritytoward the reflective slat 520. Similarly, the traces around the pegs544 a-b of the second pair of electromagnets 544 can be wound inopposite directions such that one has north magnetic polarity toward thereflective slat 520 and the other has south magnetic polarity toward thereflective slat 520.

By energizing the pair of electromagnets 542 (or 544) to have oppositepolarities as discussed herein the induced magnetization of thereflective slat 520 can complete a magnetic circuit substantiallyconfined to the region nearest the pair of electromagnets 542 (or 544).For example, in an example where the pegs 542 a-b (or 544 a-b) areseparated by a distance d_(pair) (i.e., the distance between the centersof the pegs 542 a-b), the induced magnetization of the reflective slat520 can extend roughly over a region characterized by the distanced_(pair). In some embodiments, the distance d_(pair) can beapproximately 2-3 millimeters. The peg 542 a is also located a distanced_(end) from the short-side end 527 of the reflective slat 520. Thedistance d_(end) can be approximately 2-3 millimeters, for example. Bysituating the pegs 542 a-b and 544 a-b relatively near the short-sideends 525, 527, the magnetic attraction from the electromagnets does notsignificantly deform the reflective surface 521 of the slat 520. Bycontrast, a single electromagnet located near the center of the sideedge 526 of the reflective slat 520 (i.e., approximately equidistantfrom the two short-side ends 525, 527) may cause the reflective surface521 of the slat 520 to deform (“flex”) near its middle area while theregions near the side edges 525, 527 did not rotate as much.

The pegs 542 a-b can each be mounted to a foundational sheet 550 tostructurally support the pegs 542 a-b. For example, the end 564 of thepeg 542 a (which is opposite the slat-facing end 562) can be coupled tothe foundational sheet 550 (e.g., by welding, soldering, adhesives,etc.). The foundational sheet 550 may be a sheet including steel oranother metal and/or ferromagnetic material. The substrate 540, whichcan be a printed circuit board, can be mounted on the foundational sheet550. The foundational sheet 550 may complete a magnetic circuit betweenthe pairs of electromagnets 542, 544. For example, energizing the pairof electromagnets 542 with opposite polarities can magnetize the regionof the foundational sheet 550 between the two pegs 542 a-b such that thetwo pegs 542 a-b are part of a magnetic circuit with opposite polaritieson the slat-facing ends of the two pegs 542 a-b.

FIG. 6A is an end view of a reflective slat 610 oriented in a nominalposition. The reflective slat 610 is mounted by a first connecting arm612 and a second connecting arm (not visible) connected to opposite endsof the reflective slat 610. The connecting arm 612 can be configured totwist to allow the reflective slat 610 to rotate about an axis ofrotation defined by the connecting arm 612. In some examples thereflective slat 610 and the connecting arm 612 can be formed from areflective, flexible, and/or magnetic material such as silicone steel,for example. In some examples the connecting arm 612 can be a narrowstrip that is integrally formed with the reflective slat 610.

An electromagnetic driving system includes an electromagnet 620 situatedto magnetically attract the reflective slat 610 at a position radiallyoffset from the axis of rotation defined by the connecting arm 612. InFIG. 6A, the reflective slat 610 is shown in a non-rotated position,which may be, for example, an orientation for which the connecting arm612 is not stressed by twisting. The non-rotated position shown in FIG.6A (which is also referred to herein as the nominal position) cantherefore be considered a resting position, because the reflective slat610 is not being urged to rotate and the connecting arm 612 is in arelaxed energy state. The non-rotated position is indicated in FIG. 6Aby a line labeled 0° indicating the orientation of the reflective slat610. The non-rotated position illustrated in FIG. 6A may occur while theelectromagnet 620 is deactivated, and therefore not attracting thereflective slat 610, for example.

FIG. 6B is an end view of the reflective slat 610 oriented in a rotatedposition due to attraction between the reflective slat 610 and theelectromagnet 620. For example, upon activation of the electromagnet 620(e.g., by conveying current through a coil surrounding a ferromagneticcore), the side of the reflective slat 610 nearest the electromagnet 620can be magnetically attracted toward the electromagnet 620. Thereflective slat 610 may include a ferromagnetic material, such as steel,that becomes magnetized in response to the activation of theelectromagnet 620 and thereby creates an attractive magnetic forcebetween the electromagnet 620 and the region of the reflective slat 610nearest the electromagnet 620. Attracting one side of the reflectiveslat 610 toward the electromagnet 620 can thus cause the reflective slat610 to rotate (e.g., by twisting the connecting arm 612). The degree ofrotation of the reflective surface of the reflective slat 610, relativeto the nominal position, is shown in FIG. 6B as angle A.

During rotation, the connecting arm 612 twists to allow the reflectiveslat 610 to rotate. However, the connecting arm 612 can apply a torqueon the reflective slat 610 to urge the reflective slat to return to thenon-rotated position (i.e., the position shown in FIG. 6A). In someexamples, the amount of torque applied by the connecting arm 612 isdependent on the amount the connecting arm 612 is twisted. For example,the connecting arm 612 may apply a torque on the reflective slat 610that is proportionate to the amount of rotation away from the nominalposition of the reflective slat 610. Moreover, the torque applied by theconnecting arm 612, when twisted, can urge the reflective slat 610 toreturn to the nominal position (i.e., 0° orientation shown in FIG. 6A).Thus, during rotation the reflective slat 610 can be subjected to forcesfrom both the electromagnet 620 and the connecting arm 612. In someexamples, the reflective slat 610 may rotate toward the electromagnet620 until a point where the torque on the reflective slat 610 applied bythe electromagnet 620 balances the torque from the twisted connectingarm 612.

FIG. 6C is an end view of the reflective slat 610 oriented in a secondrotated position due to the reflexive torque applied by the connectingarm 612. The degree of rotation of the reflective surface of thereflective slat 610, relative to the nominal position, is shown in FIG.6C as angle B. The rotated position of the reflected slat 610 shown inFIG. 6C may occur following deactivation of the electromagnet 620. Forexample, the connecting arm 612 can become twisted during an initialattraction toward the electromagnet 620 (as shown in FIG. 6B). Once theelectromagnetic attraction is turned off or decreased, the reflectiveslat 610 can rotate according to the force applied by the twistedconnecting arm 612. The reflective slat 610 can be initially urged backtoward the nominal position (as shown in FIG. 6A). Upon reaching thenominal position, the reflective slat 610 can then continue itsrotational inertia to move through the nominal position, which causesthe connecting arm 612 to twist in the opposite direction of that shownin FIG. 6B. Once twisted, the connecting arm 612 can apply a torqueurging the reflective slat 610 toward the nominal position. Thereflective slat 610 can continue rotating away from the electromagnet620 until its direction of rotation is reversed by the twistedconnecting arm 612.

Thus, the three views in FIGS. 6A-6C may represent portions of anelectromagnetic driving sequence of the reflective slat 610. Forexample, FIG. 6A may illustrate the rest orientation of the reflectiveslat 610, where the connecting arm 612 is in an unstressed state and theelectromagnet 620 is turned off. FIG. 6B may illustrate the reflectiveslat 610 at a maximum angle of deflection toward the electromagnet 620(e.g., the angle A). FIG. 6C may illustrate the reflective slat 610 at amaximum angle of deflection away from the electromagnet 620 (e.g., theangle B).

In some embodiments, the driving system may include more than oneelectromagnet situated to attract the reflective slat and may includemore than one reflective slat, such as an example with fourelectromagnets for each reflective slat.

FIG. 7 is a view of an example beam-steering device 700 with multipleoscillating reflective slats 720. The beam-steering device 700 includesa frame 710 with a first side 712 and a second side 714. Each of thereflective slats 720 a-1 is mounted to the two sides 712, 714 of theframe 710 by connecting arms that are coupled between opposite sides ofthe reflective slats 720 a-1 and each of the sides 712, 714. Forexample, the first reflective slat 720 a is mounted by a firstconnecting arm 722 and a second connecting arm 724. The first connectingarm 722 is connected to a mid-point of one end of the reflective slat720 a and the side 714 of the frame 710. The second connecting arm 724is connected to a mid-point of the opposite end of the reflective slat720 a and the side 712 of the frame. Thus, the reflective slat 720 a issuspended between the sides 712, 714 of the frame 710 by connecting arms722, 724 connected to mid-points of opposite ends of the reflective slat720 a. In some examples, the connecting arms 722, 724 can be narrowstrips that are integrally formed with the reflective slat 720 a. Eachof the reflective slats 720 b-1 can also be mounted to the frame 710 byconnecting arms connected to mid-points of opposite ends of thereflective slats 720 b-1. The connecting arms twist to allow each of thereflective slats 720 a-1 to rotate about an axis of rotation defined bythe pairs of connecting arms.

The axes of rotation of the reflective slats 720 a-1 defined by therespective pairs of connecting arms (e.g., the connecting arms 722, 724)are all situated in a common plane and oriented in parallel. Thereflective slats 720 a-1 are arranged in an array with a single row, andthe axes of rotation of the reflective slats 720 a-1 can beperpendicular to the direction of the row. The reflective slats 720 a-1can be oscillated about their respective axes of rotation to cause anincident pulse of light to be jointly reflected by the reflective slats720 a-1 and re-directed according to the instantaneous orientation ofthe reflective slats 720 a-1. The moment of inertia of the individualreflective slats 720 a-1 is relatively small compared to, for example,the moment of inertia of a single mirror with a reflective surfaceapproximately equal to the cumulative reflective surfaces in the arrayof reflective slats 720. Moment of inertia is related to resonantfrequency, with lower moments of inertia corresponding to higherresonant frequencies and vice versa. The array of reflective slats 720a-1 can therefore be driven to oscillate at a relatively higherfrequency than a single mirror with a comparable cumulative reflectivesurface area.

In some embodiments, the reflective slats 720 a-1 can be driven with anelectromagnetic driving system of electromagnets situated underneath thearray of reflective slats 720 to cause the reflective slats 720 a-1 tooscillate in phase. For example, each of the reflective slats 720 a-1can be associated with a group of electromagnets arranged to applytorque on the reflective slat by magnetically attracting the reflectiveslat. Each reflective slat 720 a-1 can have a mirror-associated set ofelectromagnets, and each mirror-associated set can be separatelyoperated to cause the array of reflective slats 720 to oscillate inphase while accounting for variation in resonant frequencies among thereflective slats 720 a-1.

In some embodiments, the array of reflective slats 720 can have anapproximate height of 3 centimeters and an approximate width of 6centimeters (e.g., each reflective slat can have dimensions of 3centimeters by 0.5 centimeters). The beam-steering device 700 can beused to direct incident light pulses with a beam diameter ofapproximately 3 centimeters, for example.

In some examples, the beam-steering device 700 can be operated tooscillate the array of reflective slats 720, in phase, by about 2°(e.g., between +1° and −1°) and at a frequency of about 5 kilohertz. Thebeam-steering device 700 can thus be used to direct incident lightpulses across a scanning region with an opening angle of about 2° withan angular scanning frequency of about 5 kilohertz, for example.

FIG. 8A is a block diagram of an electromagnetic driving system 800 foran example beam-steering device with multiple oscillating mirrors 810,820. The system 800 includes an orientation feedback system 830, acontroller 840, and a memory 844. The controller 840 instructs anelectromagnetic driving system to cause the mirrors 810, 820 tooscillate. The mirrors 810, 820 may be similar to the reflective slatsdiscussed in connection with FIGS. 5 and 6 above, and may be part of anarray of such reflective slats. For example, the electromagnetic drivingsystem can include an electromagnet 814 (or multiple electromagnets)associated with mirror 810 and an electromagnet 824 (or multipleelectromagnets) associated with mirror 820. A first driving circuit 816operates the electromagnet 814 according to input 818 from thecontroller 840, and a second driving circuit 826 operates theelectromagnet 824 according to input 828 from the controller 840. Thedriving circuits 816, 826 can each generate driving signals, such as asinusoidal alternating current or other time-varying current, toenergize the respective electromagnets 814, 824 associated with each ofthe mirrors 810, 820. When driven, the electromagnets 814, 824 can causethe mirrors 810, 820 to oscillate about their respective axes ofrotation (e.g., the axes of rotation defined by twisting the connectingarms 812, 822).

The orientation feedback system 830 can include detectors for sensingthe position (“orientation”) of the mirrors 810, 820 and providinginformation indicative of the positions to the controller 840. Thecontroller 840 can analyze the information from the orientation feedbacksystem 830 to identify phase differences and/or amplitude differencesbetween the oscillatory motion of the different mirrors in the array.The controller 840 can then adjust the inputs 818, 828 supplied todriving circuits 816, 826 associated with the mirrors 810, 820 toaccount for the detected differences in phase and/or amplitude. Forexample, the inputs 818, 828 can include respective amplitude and phaseinformation sufficient to cause the mirrors 810, 820 (and any additionalmirrors in the array) to oscillate substantially in phase and with asubstantially similar amplitude. Inputs 818 and 828 can includedifferent amplitude and phase information to account for differentcharacteristics of mirrors 810 and 820.

In this regard, even when driven with identical driving currents, thetwo mirrors 810, 820 may oscillate with a difference in phase and/oramplitude. The two mirrors 810, 820 may have different moments ofinertia and/or resonant frequencies due to variations in dimensions,mass, axis alignment, and/or material stiffness, etc., of the mirrors810, 820 and/or connecting arms 812, 822. Moreover, the placement of theelectromagnets 814, 824 with respect to the mirrors 810, 820 caninfluence the efficacy of the magnetic attraction (i.e., the magneticcoupling) for a given driving current of the electromagnets 814, 824. Insome examples, the moments of inertia, resonant frequency, and/ormagnetic coupling of the two mirrors 810, 820 may differ due tomanufacturing variations in dimensions, mass distribution, materialstiffness, etc. among the mirrors 810, 820, the connecting arms 812,822, and/or the electromagnets 814, 824.

Differences in moments of inertia and/or resonant frequencies result inphase offsets and/or amplitude variations in oscillatory motion betweena group of harmonic oscillators driven with a common driving signal. Forinstance, for a torsional harmonic oscillator driven to oscillate at adriving frequency f_(drive) by a sinusoidal driving force of the form:F(t)=A ₀ sin(2π(f _(drive))t),the angular orientation of the oscillator as a function of time is givenby:θ(t)=A sin(2π(f _(drive))t+ϕ)where A is the amplitude of the oscillatory motion and ϕ is a phaseoffset (“phase delay”) between the driving force and the resultingoscillatory motion. Both the amplitude A and the phase offset ϕ can bedependent on one or more of the driving frequency, the moment of inertiaof the oscillator, and the resonant frequency f_(res) of the oscillator.

While the amplitude and phase delay may therefore be substantiallyunique according to characteristics of the oscillator (e.g., massdistribution, material stiffness, dimensions, axis orientation, etc.),some embodiments of the present disclosure present techniques foradjusting the amplitude and/or phase delay. In some examples, the phaseoffset of such a driven harmonic oscillator can be modified by adjustingthe phase of the driving signal. The phase of the driving signal canthen at least approximately add to the phase delay of the harmonicoscillator to provide a desired phase. Thus, the phase of the drivingsignal can be approximately added to the observed phase offset of agiven harmonic oscillator to generate a predetermined phase of theresulting oscillatory motion.

In some examples, the amplitude of the oscillatory motion of such adriven harmonic oscillator can be modified by adjusting the amplitude ofthe driving force. The driving force amplitude adjustments may result inapproximately proportionate adjustments in the amplitude of theoscillatory motion, particularly for a driving frequency that is notnear the resonant frequency of the oscillator. Thus, the amplitude A ofthe oscillatory motion may be approximately proportionate to theamplitude A₀ of the driving force F(t). The phase delay of theoscillatory motion can also be modified by introducing a correspondingphase offset on the driving force. For example, where the driving forceis changed to:F _(adj)(t)=A _(adj) sin(2π(f _(drive))t+ϕ _(adj)).the oscillatory motion of the oscillator can change to:θ(t)=(A _(adj) /A ₀)A sin(2π(f _(drive))t+ϕ _(adj)+ϕ).

The values of A_(adj) and/or θ_(adj) may therefore be selected toachieve a predetermined amplitude and/or phase delay of the oscillatorymotion. That is, once the values of A and 0 are observed (or otherwiseidentified), the values of A_(adj) and θ_(adj) can be selected toprovide oscillatory motion with a desired amplitude and/or phase.

Some embodiments of the present disclosure therefore provide for thecontroller 840 to receive information from the orientation feedbacksystem 830 indicating the orientations of the mirrors 810, 820. Themirror orientations may be sensed via optical detection systems,encoders, inductive proximity measurements, etc. The orientationfeedback system 830 may include, for example, detecting distancesbetween a portion of the mirrors 810, 820 and a fixed sensor (e.g., aproximity sensor). The controller 840 can then determine an amplitudeand/or phase offset to apply to the driving signals of one or more ofthe electromagnets (e.g., the electromagnets 814, 824) in theelectromagnetic driving system to cause the mirrors 810, 820 tooscillate in phase. For example, the controller 840 may determine anamplitude A₁ and phase ϕ₁ apply to the driving signals for the firstmirror 810; an amplitude A₂ and phase ϕ₂ to apply to the driving signalsfor the second mirror 820; and so on. The controller 840 can convey theamplitude and/or phase information for the first and second mirrors 810,820 in inputs 818, 828 to the respective driving circuits 816, 826 forthe electromagnets 814, 824. The driving circuits 816, 826 can thenapply suitable currents to energize the electromagnets 814, 824according to the amplitude and/or phase delay information (e.g., A₁, ϕ₁,A₂, ϕ₂, etc.) provided in the respective inputs 818, 828.

In some examples, a memory 842 in communication with the controller 840can store indications of the driving parameters 844 for each mirror 810,820. The indications of the driving parameters 844 are represented inFIG. 8A by a lookup table for purposes of illustration only. In someexamples, the controller 840 may operate to intermittently update thedriving parameters 844 stored in the memory 842. In some examples, thecontroller 840 may determine new values for the driving parameters 844based on real-time analysis of the information from the orientationfeedback system 830.

To ease the computation burden between updates, the system 800 cancontinue to operate with the most recently determined drivingparameters. For example, the driving parameters 844 may be updated at afrequency of 10 hertz, or another frequency that is less than thedriving frequency. The controller 840 may be implemented as aproportional-integral-derivative (PID) controller, for example, thatoperates to periodically adjust the amplitudes and/or phases of thedriving signals of each mirror 810, 820 based on information from theorientation feedback system 830.

Thus, the controller 840 can control the mirrors 810, 820 (and anyadditional mirrors in the array) to oscillate in a coordinated fashionso as to jointly steer incoming light pulses according to the commonorientation of the mirrors 810, 820. In some embodiments, the mirrors810, 820 (and any additional mirrors) can be driven to oscillateapproximately in phase and with an approximately equal amplitude suchthat incoming pulses of light are scanned cross a scanning zone with anopening angle corresponding to the angular oscillations of the mirrors810, 820 (i.e., the amplitude of the oscillatory motion).

FIG. 8B is a block diagram of an electromagnetic driving system 801 thatincludes inductance sensors 850, 852 to detect the orientation of themultiple oscillating mirrors 810, 820. The inductance sensors 850, 852operate to measure the inductance of the conductive coils of theelectromagnets 814, 824. The inductance measurement can be used todetermine the distance between the end of the electromagnets 814, 824and the bottom side of the mirrors 810, 820 (e.g., the distance d_(gap)between the end of the core of the electromagnet 814 and the bottom sideof the mirror 810 as shown in FIG. 8B). In some examples, the inductancevalue is linearly proportional to the distance between theelectromagnets 814, 824 and the mirrors 810, 820. The inductance sensors850, 852 can therefore be used to sense the positions of the mirrors810, 820 relative to the electromagnets 814, 824. Position information851, 853 is output from the inductance sensors 850, 852 to thecontroller 840 and used to determine driving parameters for the mirrors810, 820. The position information 851, 853 output from the inductancesensors 850, 852 may be, for example, inductance values, and thecontroller 840 may be configured to map the inductance values toorientations of the mirrors 810, 820 (e.g., according to look-up tables,calibration information, etc.). The inductance sensors 850, 852 on theelectromagnets 814, 824 in the system 801 are one example of anorientation feedback system.

It is noted that the block diagrams in FIGS. 8A and 8B each include twomirrors 810, 820 and two electromagnets 814, 824, although this is forpurposes of illustration and explanation only. In some embodiments, thefunctions of the controller 840 and/or orientation feedback system 830may be applied to systems with an array of oscillating mirrors ofarbitrary size and/or number. Moreover, each oscillating mirror in suchan array may be driven by more than one electromagnet and may be drivenby oscillatory systems other than an electromagnetic driving system. Forexample, each mirror in the array may be driven by four electromagnetsassociated with each mirror, similar to the arrangement described inconnection with FIG. 5D above.

In addition, it is noted that the block diagrams in FIGS. 8A and 8B arenot intended to illustrate the relative scale or dimensions of thevarious physical features, such as the mirrors 810, 820. For example, insome embodiments the mirrors 810, 820 may be spaced relative to oneanother at a minimum separation distance while still allowing for enoughroom for clearance while the two mirrors oscillate with respect to oneanother (and may also include enough room to account for manufacturingand/or engineering tolerances). In particular, minimizing the separationdistance between adjacent ones of the oscillating mirrors (e.g., themirrors 810, 820) allows for the total combined reflective surface areaof the array of mirrors to be maximized.

FIG. 9A is a flowchart of a process 900 for operating a beam-steeringdevice with multiple oscillating mirrors according to an exampleembodiment. Sets of electromagnets can be associated with each of theoscillating mirrors for operating each of the mirrors. Each set ofmirror-associated electromagnets can be operated by a respective drivingcircuit based on respective input (902). Data indicative of detectedorientations of the mirrors can be received (904). For example,orientation information can be received from an orientation feedbacksystem. Driving parameters sufficient to cause the driving circuits tooperate the electromagnets such that the mirrors oscillate in phase atan operating frequency can be determined (906). For example, acontroller can analyze the orientation information received in block 904to determine phases and/or amplitudes of driving signals to apply to theelectromagnets to cause the mirrors to oscillate in phase. Thedetermined driving parameters can be provided as inputs to the drivingcircuits (908).

FIG. 9B is a flowchart of a process 920 for operating a light detectionand ranging (LIDAR) device according to an example embodiment. The LIDARdevice can include a light source and a plurality of mirrors. Pulses oflight can be emitted from the light source toward the plurality ofmirrors to be emitted from the LIDAR device (922). The pulses of lightmay be reflected by the plurality of mirrors to scan across a scanningzone, for example. The light pulses can be reflected by, for example, anarray of mirrors oscillating in phase at an operating frequency tojointly reflect incident light pulses according to the orientation ofthe mirrors in the array. The plurality of mirrors may be operatedaccording to the process 900 described in connection with FIG. 9A above.Returning reflected light signals corresponding to the emitted lightpulses can be received (924). Obstacles in the scanning zone can beidentified based on the returning reflected signals and based onorientations of the plurality of mirrors in the LIDAR device at the timethe pulses of light were emitted (926). The orientation of the mirrorsin the LIDAR device can be, for example, the orientation of an array ofmirrors. An autonomous vehicle associated with the LIDAR device can thenbe controlled to avoid the identified obstacles (928). The autonomousvehicle may be controlled, for example, by the navigation/pathing system142 and/or obstacle avoidance system 144 discussed in connection withthe autonomous vehicle 100 of FIG. 1.

FIGS. 9A and 9B present flowcharts describing processes employedseparately or in combination in some embodiments of the presentdisclosure. The methods and processes described herein are generallydescribed by way of example as being carried out by an autonomousvehicle, such as the autonomous vehicles 100, 200 described above inconnection with FIGS. 1 and 2. For example, the processes describedherein can be carried out by the LIDAR sensor 128 mounted to anautonomous vehicle in communication with the computer system 112, sensorfusion algorithm module 138, and/or computer vision system 140.

Furthermore, it is noted that the functionality described in connectionwith the flowcharts described herein can be implemented asspecial-function and/or configured general-function hardware modules,portions of program code executed by a processor (e.g., the processor113 in the computer system 112) for achieving specific logicalfunctions, determinations, and/or steps described in connection with theflowcharts. Where used, program code can be stored on any type ofcomputer readable medium (e.g., computer readable storage medium ornon-transitory media, such as data storage 114 described above withrespect to computer system 112), for example, such as a storage deviceincluding a disk or hard drive. In addition, each block of theflowcharts can represent circuitry that is wired to perform the specificlogical functions in the process. Unless specifically indicated,functions in the flowcharts can be executed out of order from that shownor discussed, including substantially concurrent execution of separatelydescribed functions, or even in reverse order in some examples,depending on the functionality involved, so long as the overallfunctionality of the described method is maintained. Furthermore,similar combinations of hardware and/or software elements can beemployed to implement the methods described in connection with otherflowcharts provided in the present disclosure.

As used herein a “scanning zone” generally refers to a region of ascanned environment scanned by a single LIDAR device, or a combinationof LIDAR devices, that is completely sampled in a complete scan by theLIDAR device. That is, for a LIDAR device operated to continuouslyactively map its surroundings for reflective features, the scanning zoneis the complete region mapped before returning to map the same pointagain. Generally, the scanning zone referred to herein is defined withreference to the point of view of the LIDAR device in terms of azimuth(e.g., angle along the horizon) and altitude (e.g., angle perpendicularto the horizon) with respect to the point of view of the LIDAR device.Thus, the geographic location mapped by the scanning zone of a LIDARdevice is not fixed, but rather moves with the LIDAR device. Forexample, the scanning zone can be considered a bubble (or cone-shapedregion, etc.) surrounding a particular LIDAR device with dimensionsdefined by the maximum distance sensitivity of the LIDAR device.

FIG. 10 depicts a computer-readable medium configured according to anexample embodiment. In example embodiments, the example system caninclude one or more processors, one or more forms of memory, one or moreinput devices/interfaces, one or more output devices/interfaces, andmachine-readable instructions that when executed by the one or moreprocessors cause the system to carry out the various functions, tasks,capabilities, etc., described above, such as the processes discussed inconnection with FIGS. 9A and 9B above.

As noted above, in some embodiments, the disclosed techniques can beimplemented by computer program instructions encoded on a non-transitorycomputer-readable storage media in a machine-readable format, or onother non-transitory media or articles of manufacture (e.g., theinstructions 115 stored on the data storage 114 of the computer system112 of vehicle 100 and/or instructions executed by the controller 316 ofthe LIDAR system 300). FIG. 10 is a schematic illustrating a conceptualpartial view of an example computer program product 1000 that includes acomputer program for executing a computer process on a computing device,arranged according to at least some embodiments presented herein.

In one embodiment, the example computer program product 1000 is providedusing a signal bearing medium 1002. The signal bearing medium 1002 mayinclude one or more programming instructions 1004 that, when executed byone or more processors may provide functionality or portions of thefunctionality described above with respect to FIGS. 1-9. In someexamples, the signal bearing medium 1002 can be a non-transitorycomputer-readable medium 1006, such as, but not limited to, a hard diskdrive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape,memory, etc. In some implementations, the signal bearing medium 802 canbe a computer recordable medium 1008, such as, but not limited to,memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations,the signal bearing medium 1002 can be a communications medium 1010, suchas, but not limited to, a digital and/or an analog communication medium(e.g., a fiber optic cable, a waveguide, a wired communications link, awireless communication link, etc.). Thus, for example, the signalbearing medium 1002 can be conveyed by a wireless form of thecommunications medium 1010.

The one or more programming instructions 1004 can be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device such as the computer system 112 of FIG. 1is configured to provide various operations, functions, or actions inresponse to the programming instructions 1004 conveyed to the computersystem 112 by one or more of the computer readable medium 1006, thecomputer recordable medium 1008, and/or the communications medium 1010.

The non-transitory computer readable medium could also be distributedamong multiple data storage elements, which could be remotely locatedfrom each other. The computing device that executes some or all of thestored instructions could be a vehicle, such as the vehicle 200illustrated in FIG. 2. Alternatively, the computing device that executessome or all of the stored instructions could be another computingdevice, such as a server.

While various example aspects and example embodiments have beendisclosed herein, other aspects and embodiments will be apparent tothose skilled in the art. The various example aspects and exampleembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting, with the true scope and spirit beingindicated by the following claims.

What is claimed is:
 1. A device comprising: a frame; a first reflectiveslat; a plurality of first-reflective-slat connecting arms connectingthe first reflective slat to the frame, wherein the plurality offirst-reflective-slat connecting arms define an axis of rotation of thefirst reflective slat; a second reflective slat; a plurality ofsecond-reflective-slat connecting arms connecting the second reflectiveslat to the frame, wherein the plurality of second-reflective-slatconnecting arms define an axis of rotation of the second reflectiveslat; a plurality of first-reflective-slat electromagnets proximate aportion of the first reflective slat and offset from the axis ofrotation of the first reflective slat, wherein the first-reflective-slatelectromagnets are configured to be activated to magnetically attractthe portion of the first reflective slat such that the first reflectiveslat rotates about the axis of rotation of the first reflective slat;and a plurality of second-reflective-slat electromagnets proximate aportion of the second reflective slat and offset from the axis ofrotation of the second reflective slat, wherein thesecond-reflective-slat electromagnets are configured to be activated tomagnetically attract the portion of the second reflective slat such thatthe second reflective slat rotates about the axis of rotation of thesecond reflective slat.
 2. The device of claim 1, wherein the framecomprises a first side rail and a second side rail opposite the secondside rail, wherein the plurality of first-reflective-slat connectingarms comprises a first connecting arm connecting the first reflectiveslat to the first side rail and a second connecting arm connecting thefirst reflective slat to the second side rail, and wherein the pluralityof second-reflective-slat connecting arms comprises a third connectingarm connecting the second reflective slat to the first side rail and afourth connecting arm connecting the second reflective slat to thesecond side rail.
 3. The device of claim 1, wherein the frame defines acommon plane, and wherein the axis of rotation of the first reflectiveslat and the axis of rotation of the second reflective slat are orientedin parallel in the common plane.
 4. The device of claim 1, wherein theplurality of first-reflective-slat connecting arms are integrally formedwith the first reflective slat and the plurality ofsecond-reflective-slat connecting arms are integrally formed with thesecond reflective slat.
 5. The device of claim 1, wherein the pluralityof first-reflective-slat connecting arms are integrally formed with theframe and the plurality of second-reflective-slat connecting arms areintegrally formed with the frame.
 6. The device of claim 1, wherein theplurality of first-reflective-slat electromagnets comprises a firstelectromagnet having a north pole facing the first reflective slat and asecond electromagnet having a south pole facing the first reflectiveslat, and wherein the plurality of second-reflective-slat electromagnetscomprises a third electromagnet having a north pole facing the secondreflective slat and a second electromagnet having a south pole facingthe second reflective slat.
 7. The device of claim 1, wherein theplurality of first-reflective-slat electromagnets comprises a first pairof electromagnets configured to define a first magnetic circuit througha first region of the first reflective slat and a second pair ofelectromagnets configured to define a second magnetic circuit through asecond region of the first reflective slat, and wherein the plurality ofsecond-reflective-slat electromagnets comprises a third pair ofelectromagnets configured to define a third magnetic circuit through athird region of the second reflective slat and a fourth pair ofelectromagnets configured to define a fourth magnetic circuit through afourth region of the second reflective slat.
 8. The device of claim 1,wherein each of the first-reflective-slat electromagnets andsecond-reflective-slat electromagnets comprises a respectiveferromagnetic peg surrounded by a respective coil.
 9. The device ofclaim 1, wherein the first and second reflective slats comprise siliconesteel.
 10. The device of claim 1, wherein the first reflective slat hasa first back surface facing the first-reflective-slat electromagnets anda first reflective surface opposite the first back surface, and whereinthe second reflective slat has a second back surface facing thesecond-reflective-slat electromagnets and a second reflective surfaceopposite the second back surface.
 11. The device of claim 1, wherein thefirst reflective slat is generally rectangular with a first lengthdimension parallel to the axis of rotation of the first reflective slatand a first width dimension perpendicular to the axis of rotation of thefirst reflective slat, wherein the second reflective slat is generallyrectangular with a second length dimension parallel to the axis ofrotation of the second reflective slat and a second width dimensionperpendicular to the axis of rotation of the second reflective slat. 12.The device of claim 11, wherein the first length dimension is greaterthan the first width dimension and the second length dimension isgreater than the second width dimension.
 13. The device of claim 1,further comprising a substrate mounted to an underside of the frame,wherein the first-reflective-slat electromagnets are disposed on thesubstrate under the first reflective slat, and wherein thesecond-reflective slat electromagnets are disposed on the substrateunder second reflective slat.
 14. The device of claim 1, wherein thefirst-reflective-slat electromagnets, when activated, exert a firstattractive magnetic force on the first reflective slat that causes thefirst reflective slat to rotate from a first non-rotated position to afirst rotated position, and wherein the second-reflective-slatelectromagnets, when activated, exert a second attractive magnetic forceon the second reflective slat that causes the second reflective slat torotate from a second non-rotated position to a second rotated position.15. The device of claim 14, wherein the first-reflective-slat connectingarms are configured to exert a first torque on the first reflective slatthat causes, when the first-reflective-slat electromagnets aredeactivated, the first reflective slat to rotate from the first rotatedposition to the first non-rotated position, and wherein thesecond-reflective-slat connecting arms are configured to exert a secondtorque on the second reflective slat that causes, when thesecond-reflective-slat electromagnets are deactivated, the secondreflective slat to rotate from the second rotated position to the secondnon-rotated position.
 16. A method, comprising: rotating a firstreflective slat about a first axis of rotation, wherein the first axisof rotation is defined by a plurality of first-reflective-slatconnecting arms that connect the first reflective slat to a frame,wherein rotating the first reflective slat about the first axis ofrotation comprises activating and deactivating a plurality offirst-reflective-slat electromagnets; and rotating a second reflectiveslat about a second axis of rotation, wherein the second axis ofrotation is defined by a plurality of second-reflective-slat connectingarms that connect the second reflective slat to the frame, whereinrotating the second reflective slat about the second axis of rotationcomprises activating and deactivating a plurality ofsecond-reflective-slat electromagnets.
 17. The method of claim 16,wherein rotating the first reflective slat and rotating the secondreflective slat comprise rotating the first and second reflective slatsin phase.
 18. The method of claim 16, wherein rotating the firstreflective slat about the first axis of rotation comprises activatingthe first-reflective-slat electromagnets such that thefirst-reflective-slat electromagnets exert a first attractive magneticforce on the first reflective slat that causes the first reflective slatto rotate from a first non-rotated position to a first rotated position,and wherein rotating the second reflective slat about the second axis ofrotation comprises activating the second-reflective-slat electromagnetssuch that the second-reflective-slat electromagnets exert a secondattractive magnetic force on the second reflective slat that causes thesecond reflective slat to rotate from a second non-rotated position to asecond rotated position.
 19. The method of claim 18, wherein rotatingthe first reflective slat about the first axis of rotation furthercomprises the first-reflective-slat connecting arms exerting a firsttorque on the first reflective slat that causes, when thefirst-reflective-slat electromagnets are deactivated, the firstreflective slat to rotate from the first rotated position to the firstnon-rotated position, and wherein rotating the second reflective slatabout the second axis of rotation further comprises thesecond-reflective-slat connecting arms exerting a second torque on thesecond reflective slat that causes, when the second-reflective-slatelectromagnets are deactivated, the second reflective slat to rotatefrom the second rotated position to the second non-rotated position. 20.The method of claim 19, wherein rotating the first reflective slat aboutthe first axis of rotation further comprises rotational inertia of thefirst reflective slat causing the first reflective slat to rotate pastthe first non-rotated position to a third rotated position, and whereinrotating the second reflective slat about the second axis of rotationfurther comprises rotational inertia of the second reflective slatcausing the second reflective slat to rotate past the second non-rotatedposition to a fourth rotated position.